<I>Ornithocercus Magnificus</I>

THECAL MORPHOLOGY OF ORNITHOCERCUS MAGNIFI- CUS (D1NOFLAGELLATA) WITH NOTES ON RELATED SPECIESl

DEAN R. NORRIS Department of Oceanography, Texas A&M University, College Station, Texas 77843

ABSTRACT Detailed descriptions of the thecal plates of Omithocercus magnificus are given. Though a few differences in structural detail are disclosed, the number and general arrangement of these plates are the same as those of Omithocercus thumi. Species in the family Ornithocercidae which are rare or previously unreported from the Gulf of Mexico include six in the genus Omithocercus, eight in Histioneis and one in Parahistioneis. Figures are included for all species found. Synonymies and general descriptions are given for those which differ from previously described specimens.

INTRODUCTION The identification of many dinoflagellate species is somewhat problem- atic. Armored forms of dinoflagellates have complex thecae which provide several morphological characters valuable in taxonomic studies. The most fundamental taxonomic features are the number and arrangement of the thecal plates. Shape of the body, lists (membranes), spines, and similar characters are of secondary importance (Graham, 1942: 6). Relationships within the group are based on thecal structures, yet relatively few papers are available with a critical analysis of the thecal plates. Little was known of the thecal morphology in the tribe Dinophysoidae until the study of Tai & Skogsberg (1934). They established that it is considerably more complex than was previously assumed. Their work was limited to the family Dinophysidae. According to Tai & Skogsberg (1934: 387-88), several earlier workers (SchUtt, Kofoid, & Calkins) indicated fewer plates than are actually present. Although Schlitt illustrated plates in the sulcal region he did not discuss them. Apparently, little significance was attached to the plate pattern and the thecal morphology in the Dino- physoidae until the study of Tai & Skogsberg. Tai & Skogsberg (1934: 388-89) added the following information about the Dinophysoidae: (1) there are several additional plates, mostly in the sulcus; (2) 17 plates are always present; (3) the plate pattern appears to form a natural foundation for establishment of genera; and (4) there appears to be no similarity between the plate patterns of the Peridinioidae

1 This study was accepted in partial fulfillment of the requirements for the degree of Master of Science in Oceanography at Texas A&M University. 176 Bulletin of Marine Science [19(1) and those of the Dinophysoidae. One additional paper on thecal morphology in the tribe Dinophysoidae is also limited to the family Dino- physidae (Nie & Wang, 1941). The only study of the thecal morphology of another family within the Dinophysoidae is for the Ornithocercidae (Nie, 1943). Nie found that the thecal plates of Ornithocercus thurni differ greatly in shape, size, and struc- ture from those of the genera in Dinophysidae, but the number and arrangement of plates are identical. He did not see an apical pore, a seem- ingly ubiquitous character among other Dinophysoidae and the Peri- dinioidae. Relatively little work has been done on the taxonomy of dinoflagellates from the Gulf of Mexico. Previous studies have been primarily distribu- tional, or ecological, or both. In his review, Graham (1954) pointed out the need for studies of dinoflagellates in the Gulf of Mexico and the neces- sity for analysis of plate patterns in the thecate forms. Only one species from the family Ornithocercidae was noted as occurring in the Gulf of Mexico (King, 1950; Davis, 1954; Graham, 1954; Curl, 1959; Simmons & Thomas, 1962). A study in 1964-65 by Enrique Balech (1967) has added greatly to the knowledge of dinoflagellates from the Gulf of Mexico. None of these papers includes a morphological analysis of thecal plates. The present work adds to the knowledge of the thecal morphology in the family Ornithocercidae. In addition, it contributes to our knowledge of several representatives of this family present in the Gulf of Mexico. Its objectives are: ( 1) to establish the thecal morphology and plate pattern in Ornithocercus magnificus (Stein) Kofoid & Skogsberg (1928), (2) to compare the morphology of this species with that of O. thurni studied by Nie (1943), and (3) to discuss additional representatives of the family Ornithocercidae occurring in the southeastern Gulf of Mexico.

MATERIALS AND METHODS

Microplankton samples taken aboard the RjV ALA MINOS during July, 1965, were used for this study. Collections were made with a 35p.-mesh microplankton net at each of eight stations (Fig. 38). Samples were pre- served in formalin (10 per cent by volume). Small quantities (approximately 1 ml) of the settled plankton were microscopically examined at a magnification of 100x to determine the species of Ornithocercidae present. This procedure was repeated until no different species appeared in the fraction. The species were tabulated by stations (Table 1). Specimens used for detailed study were transferred via micropipette and examined at magnifications of 450x, lOOOx, and sometimes at 1124x. Measurements were made at 450x, using an ocular mi- crometer. The method of measuring Ornithocercus was that of Kofoid & 1969] Norris: Thecal Morphology of Ornithocercus magnificus 177

TABLE 1 LIST OF DINOFLAGELLATES OBSERVED IN THE SOUTHERN PORTION OF THE GULF OF MEXICO, AND RECORD OF OCCURRENCE BY STATIONS (See Fig. 38) -- Stations 2 4 7 14 16 18 20 23 Histioneis dolon + + H. hippoperoides + H. longicollis + + + H. pacifica + + H. panaria + + H. panda + + + H. paulseni + H. variabilis + Ornithocercus carolinae + + + O. heteroporus + + + + O. magnificus + + + + + + + + O. quadratus + + + + + + + O. splendidus + + + ...L O. steini + + + + + I + + O. thurni + + + + + + + + O.sp. +1 +2 Parahistioneis para/ormis +

1 Schizont, probably O. Ihurni (Fig. 16). "Schizont, probably O. magnifierlS (Fig. 17). Skogsberg (1928: 208). Terminology and measurements of Histioneis and Parahistioneis are after Kofoid & Skogsberg (1928: 612). Methods followed in the analysis of the plates of Ornithocercus magnificus were those described by Tai & Skogsberg (1934: 385-86) and Graham (1942: 3-4). Briefly these consisted of: the use of glycerin jelly (or glycerin) as a temporary mounting medium to facilitate the making of draw- ings; the manipulation of specimens with a microneedle prepared from a piece of spun glass; the staining of some specimens with trypan blue; and dissection by application of a small amount of sodium hypochlorite (5.25 per cent by weight). A little pressure on the cover glass expedited the separation of plates. The terminology used for the plates is that of Tai & Skogsberg as modified by Balech (personal communication). The thecal description closely follows standard form. Figures, made with the aid of a camera lucida, are given for all species of Omithocercidae found in this study. Besides Ornithocercus magnificus, the only species described or discussed are the very rare ones in the genera Parahistioneis and Histioneis. They merit this attention, as little is known concerning their variations. The species of Ornithocercus not described were given an adequate general description by Kofoid & Skogsberg (1928). The principal features of Ornithocercus are illustrated in Figure 1. 178 Bulletin of Marine Science [19(1) 1

ACL---

PC L-----

----fp ---S

,~ ------RSL

---LSL

FIGURE 1. Semidiagrammatic figure illustrating principal features of Orni- thocercus, right ventral view. (ACL, anterior cingular list; C, cingulum; E, epitheca; fp, flagellar pore; H, hypotheca; LSL, left sulcal list; PCL, posterior cingular list; RSL, right sulcal list; S, sulcus)

THECAL MORPHOLOGY OF Ornithocercus magnificus (STEIN) KOFOID & SKOGSBERG (1928) General Shape.-The body (theca) is relatively small to medium, sub- circular in lateral view and deepest near the middle. In ventral view the body is subelliptical, widest at the middle, well rounded posteriorly and narrowly rounded-conical anteriorly. In apical view, the epitheca appears 1969] Norris: Thecal Morphology of Ornithocercus magnificus 179 subrectangular (Fig. 2); the dorsoventral length is greater than the lateral length. In lateral view, the epitheca is about V:J to 1h as deep as the hypotheca, slightly convex to flat, and somewhat inclined ventroposteriorly (Figs. 11-13). The cingulum (girdle) is located anteriorly as a result of the nearly flat epitheca. This groove is distinctly wider dorsally than ventrally. The dorsal width is :14 to % the greatest depth of the body, the ventral width is about % to 1f2 the dorsal width. Dorsally the cingulum is slightly concave to slightly convex, ventrally it is usually gently convex to flat. If not compressed laterally, the hypothec a would be almost a perfect hemisphere. The sulcus is about half as long as the hypotheca and somewhat impressed. Thecal Plates.-The theca is composed of seventeen plates, as it is in Ornithocercus thurni and in all species studied in the family Dinophysidae. The epitheca is made up of five plates, the cingulum four, the hypotheca four, and the sulcus four. The epithecal plates (Figs. 2-4) are: the left and right dorsal epithecal plates (Ez and Es), the left and right ventral epithecal plates (El and E~), and the pore plate (P). The two dorsal epithecal plates, being relatively large, make up most of the epitheca. They are connected by a zigzag sagittal suture and together are subrectangular in apical view. Ventrally, each dorsal plate has a small notch. The notch of the left plate (E2) is somewhat deeper and is filled by the pore plate and the left ventral epithecal plate. The notch of the right plate (Es) is occupied by the right ventral epithecal plate. Each dorsal epithecal plate possesses one row of pores and a broad membranous list, the anterior cingular list, along its lateral edge. Each list has several simple main ribs. Distally, one to several incomplete ribs can be seen between the main ribs. Reticulation may be present in the lists. The pore plate (P) is minute, subrectangular to elliptical. It lies in the ventral notch of E2 and also connects with a smalI portion of the suture line of E;{. No pore is present in the pore plate. An apical pore is present at the left ventral edge of the pore plate, and is enclosed by the pore plate, the left dorsal, and the left ventral epithecal plates.

The ventral epithecal plates are very small. The left one (El) touches the other four epithecal plates. It is situated ventral to P in the notch of

E2• The right one (E~) is in the ventral notch of Ex. Ventrally these plates are inclined posteriorly to meet the sulcal plates. Each ventral epithecal plate has a subrectangular list which connects with the list of the partner as well as with the list of the corresponding dorsal epithecal plate. These two small lists could not be distinguished when viewed laterally. One pore has been seen in each plate. The four cingular plates (Fig. 5) are: the left and right dorsal cingular 180 Bulletin of Marine Science [19(1)

2 3 4 ltJJ

o j o----E E3---: o 2

p.--- a.p.

E:j-- .0 --E,

H-- 1

FIGURES 2-10. Thecal plates of Ornithocercus magnificus, illustrating most of them after dissection: 2, epitheca from above, with omission of the list; 3, the two dorsal epithecal plates; 4, the two ventral epithecal plates; 5, the four cingular plates; 6, the same left dorsal cingular plate as in Figure 5, but in a different position allowing a rare spine to be seen; 7, the two dorsal hypothecal 1969] Norris: Thecal Morphology oj Ornithocercus magnificus 181

plates (C2 and Ca), and the left and right ventral cingular plates (C1 and C1). They are arranged in an incomplete transverse ring. The ring is dis-

tinctly wider dorsally than ventrally. Dorsally, C2 and Ca are connected by a serrated suture; ventrally, the space between C1 and C4 is filled by the right, left, and anterior sulcal plates (Fig. 10).

The two dorsal cingular plates (C2 and C3) are larger than the ventral ones. They are nearly mirror images of each other, are wide dorsally and gradually narrow as they approach the ventral side. Two distinct rows of pores, one each near the anterior and posterior margins, are present on both plates. Other pores are scattered or may form a row between the marginal rows. The two ventral cingular plates are small and subrectangular to sub- triangular in shape. The left plate (C1) is the larger and is more triangular. Pores are present in both and are mostly submarginal. The four hypothecal plates (Figs. 7-9) are: the left and right dorsal

hypothecal plates (H2 and Ha), and the left and right ventral hypothecal plates (H1 and H1). The dorsal hypothecal plates are the largest plates of the theca and dominate the shape of the body. In the left one (H2) there is a notch at the ventroanterior corner, into which fits the left ventral hypothecal plate (Hd. The right plate (Ha) has a long notch extending from the ventral side, posteriorly, to the dorsoposterior corner. This notch is filled by the

right ventral hypothecal plate (H1), the posterior sulcal plate, and the right sulcal plate. The dorsal hypothecal plates are joined together only at the dorsal side from the base of the triangular list anteriorly. Their ventral and posterior margins are separated by the left and right ventral hypothecal plates and the sulcal plates. H2 and Ha maintain well-developed lists. H2 has along its anterior edge a simple ribbed list known as the left posterior cingular list. Ventrally, this list is attached to the anterior edge of the list of H1' Similarly, H3 is provided with a list along its anterior edge, the right posterior cingular list. This list continues in a reduced form as the right sulcal list along the ventral margin to a point at or near the fisson rib. This

+- plates; 8, 9, the two ventral hypothecal plates; 10, the sulcal plates with the two ventral cingular plates, showing their relative positions in situ. (C1, left ventral cingular plate; C2, left dorsal cingular plate; Ca, right dorsal cingular plate; C1, right ventral cingular plate; E1, left ventral epithecal plate; E2, left dorsal epithecal plate; E3, right dorsal epithecal plate; E4, right ventral epithecal plate; HJ> left ventral hypothecal plate; H2, left dorsal hypothecal plate; Ha, right dorsal hypothecal plate; H4, right ventral hypothecal plate; P, pore plate; S'P anterior sulcal plate; SI, left sulcal plate; Sp, posterior sulcal plate; Sr, right sulcal plate; a-e, ribs of right ventral hypothecal plate; a.p., apical pore; f.r., fission rib.) 182 Science

561'

17 18 19 20

~ 401' 401' ~

21 22 23 1969J Norris: Thecal Morphology of Ornithocercus magnificus 183 posterior extension was observed only after dissection. H3 also possesses a small triangular list at its dorsoposterior corner. Both dorsal hypothecal plates are areolate over most of their surfaces. The areoles are subuniform and moderate to small; each has a pore at the center. In addition, a row of pores is present submarginally around both plates. A row of somewhat larger areoIes borders the dorsal hypothecal plates anteriorly. The ventral hypothecal plates are narrow, and short to rather elongate. They are most readily recognized by their lists. The left plate (Hi) is short and is embedded in the ventral notch of H2• Its right lateral margin connects with the posterior sulcal plate by the sagittal suture. The right plate (H4) is rather elongate and rests in the notch of H3, beginning almost immediately behind Hi and extending posteriorly to end at the base of the triangular list. Its left lateral margin connects to H2 by the sagittal suture. Each ventral hypothecal plate possesses pores and a list. The pores are arranged more or less in a row. The list of the left plate is the anterior portion of the left sulcal list; its distal margin may be slightly concave to convex or gently sigmoid. Irregular ribs may be present. The list of the right plate forms the posterior portion of the left sulcal list. It is charac- terized by the presence of three narrow, subuniform lobes: the posteroventral, antapical, and posterodorsal. Between the lobes, the posterior margin is always concave. The list is supported typically by five radial ribs behind the fission rib. There may be a distal submarginal rib, which is rarely complete. Reticulation is usually developed from the ribs in the posterior lobes; it varies in amount present and may be absent in young specimens. Of the five supporting ribs (Fig. 9), the a-rib (dorsal rib) extends to the posterodorsallobe; the b- and c-ribs usually end dorsal to the vertex of the antapical (middle) lobe, but the c-rib may end at or in front of this point (Figs. 11-13); the d- and e-ribs end dorsal to the posteroventral lobe. The submarginal rib extends from the posteroventral lobe to the fission rib and continues with it. Sometimes less than five main ribs are present (Fig. 12); other times one or more accessory ribs are inter- polated (Fig. 13). In young specimens, these ribs are rather simple; apparently with age they develop side branches, to such an extent that reticulation occurs. The widest point of the left sulcal list is generally at the posteroventral lobe.

~ FIGURES 11-23. Species of Ornithocercus.-11-15, O. magnificus, showing some variations. 11-14 are in left lateral view; 15 is in right lateral view; the cingular lists are distorted in 14, due to the pressure of the cover glass.-16, schizont of O. thurni (?), left lateral view.-17, schizont of O. magnificus (?), right lateral view.-18, O. carolinae, left lateral view.-19, O. heteroporus, right lateral view.-20, O. quadratus, right lateral view.-21, O. splendidus, left lateral view.-22, O. steini, right lateral view.-23, O. thurni, right lateral view. 184 Bulletin of Marine Science [19(1) The four sulcal plates (Fig. 10) are: the anterior sulcal plate (Sa), the left sulcal plate (SI), the right sulcal plate (Sr), and the posterior sulcal plate (S,,). The anterior sulcal plate (Sa) is narrow, slightly sigmoid on the left edge, and possesses an inwardly directed process at the right posterior corner. The left anterior corner is extended anteriorly. This plate is overlapped posteriorly by the left sulcal plate; measurements made in the separated state indicate that it is in contact with the flagellar pore. Anteriorly, it touches the left (El) and possibly the right ventral epithecal plate (E~); laterally, it connects to the left ventral cingular plate (Cl) and the right sulcal plate (SI')' There is no pore present. The left sulcal plate (SI) frames the left anterior portion of the flagellar pore, is small, irregularly crescent shaped, and has an inwardly directed process at the right anterior corner. It overlaps So; the processes of these two plates appear to extend together. Laterally, Sl connects with the left ventral hypothecal (Hl), left ventral cingular (Cl), and right sulcal (5,.) plates. There is no pore present. The right sulcal plate (SI') is larger than either Sa or St. It possesses an inwardly directed process at its right posterior corner. Anteriorly, it touches the right ventral epithecal plate (E4); laterally, it touches the right ventral cingular (C4), right dorsal hypothecal (Ra), and the anterior and left sulcal plates. Its narrow posterior projection is joined to the right anterior end of the posterior sulcal plate (S\I) and thus forms the right anterior portion of the flagellar pore. Along its right margin there may be a slight indication of a narrow list. One pore is present near the right margin. The posterior sulcal plate (S,,) is the largest of the group and forms the posterior half of the flagellar pore. It is elongate, somewhat concave, and has an inwardly directed process at its right anterior corner. Posteriorly, it connects with the right ventral hypothecal plate (R~). Its left side joins the left ventral hypothecal plate (Rd with the zigzag sagittal suture, while the right side joins the right dorsal hypothecal plate (Ra). There is a single longitudinal row of pores present.

Dimensions.-Length of body, 36-48 J-t; total length, 63-88 J-t; epithecal depth, 15-20 J-t; hypothecal depth, 36-45 J-t; maximum width of the left sulcal list, 32-48 J-t.

Parahistioneis Kofoid & Skogsberg Parahistioneis paraformis Kofoid & Skogsberg Fig. 24

Parahistioneis paraformis Kofoid & Skogsberg, 1928: 598, fig. 93:4; pI. 19, figs. 3, 6.-Rampi, 1947: 4, fig. 3; 1950: 4, fig. 1O.-Wood, 1963a: 13, fig. 38. 1969] Norris: Thecal Morphology of Ornithocercus magnificus 185

This individual differs from previously described specimens in being smaller and by the presence of a marginal rib along the posterior left sulcal list. Dimensions.-Length of body, 32 p.; total length, 54 p.; depth of body, 28.5 p.. Histioneis Stein Histioneis dolon Murray & Whitting Fig. 25 Histioneis d%n Murray & Whitting, 1899: 335, pI. 33, fig. 5-Kofoid & Skogsberg, 1928: 698, fig. 96:6.-Balech, 1962: 138, pI. 18, fig. 261.- Wood, 1954: 215, fig. 72; 1963a: 14, fig. 46. The body is short saddle-shaped in lateral view and somewhat higher dorsally than ventrally. The anterior cingular list is elongated, funnel shaped and striated in the distal half, and more or less well reticulated anteriorly. The left posterior cingular list has an irregular, wide-meshed reticulum in the frill and a well-developed secondary frill with several longitudinal ribs. The right posterior cingular list is not as distinctly marked. Small lateral lobes are present. The left sulcal list is slightly convex, oblique, fairly well marked, and has two to several submarginal ribs and some reticulation. The lateral fin near Ra (posterior main rib) is fairly large and possesses concentric striations. R2 (11sson rib) and Ra are somewhat sigmoid. These three specimens are smaller than those described in previous papers. They differ mainly in the proportionally lesser expansion of the distal part of the anterior cingular list. Dimensions.-Length of body, 25-26 p.; total length, 96-102 p.; depth of body, 32-36 p.; height of midbody, 19-24 p.; height of anterior cingular list, 48 p.; height of posterior cingular list, 39 p..

Histioneis hippoperoides Kofoid & Michener Fig. 26 Histioneis hippoperoides Kofoid & Michener, 1911: 296.-Kofoid & Skogs- berg, 1928: 701, fig. 96:5; pI. 23, figs. 1, 3.-Wood, 1954: 214, fig. 70. The body is short saddle-shaped in lateral view, somewhat higher dorsally than ventrally. The anterior cingular list is elongated, tubular, with weak striations and relatively little expansion anteriorly. The posterior cingular list has a strong cross-rib and distinct secondary frill on the left side only; there is a little weak reticulation in the anterior region and a somewhat irregular anterior margin. Proximally, this list has small lateral lobes. The left sulcal list is slightly convex, oblique, has weak markings, and a large indentation near R2 which is probably due to immaturity. The 186 Bulletin of Marine Science [19(1)

26 24

30.u

27 28 29 30

30u 30>J 20>J ,

FIGURES 24-30. 24, Parahistioneis paraformis, left lateral view; 25, Histioneis dolon, left lateral view; 26, H. hippoperoides, right lateral view; 27, H. longicollis, right lateral view; 28, H. pacifica, right lateral view; 29, H. panaria, right lateral view; 30, H. panaria, ventral view of another specimen. lateral fin near R;> is very similar to the one shown by Kofoid & Skogsberg

(plate 23, fig. 1). R2 is somewhat curved posteriorly; R~is sigmoid. This specimen approaches H. milneri and H. helenae. It is somewhat smaller and less developed than the type-specimen.

Dimensions.-Length of body, 23 p,; total length, 90 p,; depth of body, 33 p,; height of midbody, 19 p,; height of anterior cingular list, 40 p,; height of posterior cingular list, 30 p.. 1969] Norris: Thecal Morphology of Ornithocercus magnificus 187 Histioneis longicollis Kofoid Fig. 27 Histioneis longicollis Kofoid, 1907: 204, pI. 16, fig. 100.-Kofoid & Skogs- berg, 1928: 677, fig. 95:7; pI. 20, fig. 5; pI. 21, fig. 5.-Rampi, 1947: 11, fig. 12.-Halim, 1960: 195, pI. 2, fig. 16.-Wood, 1963a: 18, fig. 54. Description of the three specimens seen agrees with those in the above references.

Dimensions.-Length of body, 21 jJ.; total length, 69-72 jJ.; depth of body, 24-26 ,...;height of anterior cingular list, 24,...; height of posterior cingular list, 18,.... Histioneis pacifica Kofoid & Skogsberg Fig. 28 Histioneis pacifica Kofoid & Skogsberg, 1928: 681, fig. 95: 12; pI. 20, fig. 8. The body is bean shaped in lateral view. The anterior cingular list is elongated relatively little; it flares widely in the distal half, has a distinct ventral notch, and possesses striations more or less parallel to the anterior margin. The posterior cingular list is hyaline except for the supporting ribs, is nearly cylindrical, and has a low, slightly flaring frill. The left sulcal list has a somewhat undulating ventral margin, is rounded posteriorly, and has a lateral fin near Ra. In front of the fission rib are a few irregular ribs; R2 is curved posterodorsally connecting to a midregion lateral branch of RJ and has a few irregular branches. RJ is somewhat curved posteriorly and has a few branches distally. Three specimens were seen; they differ from the type in the position and the more simple distal end of Ra. Also, the dense rows of pores in and near the cingulum spoken of in Kofoid & Skogsberg, p. 683, were not observed. Dimensions.-Length of body, 19.5-22,...; total length, 55-62,...; depth of body, 27-29,...; height of anterior cingular list, 21-22,...; height of posterior cingular list, 14-16 jJ..

Histioneis panaria Kofoid & Skogsberg Figs. 29-30

Histioneis panaria Kofoid & Skogsberg, 1928: 659, figs. 85:8, 9; 95:6.- Wood, 1963b: 6, fig. 17. The two specimens seen differ from previously described individuals, in that R2 bends posterodorsally to form a rib near the ventral edge of the left sulcal list. This rib is fused or nearly fused to the distal end of Ra. A right lateral fin near RJ was also observed. This hyaline fin could easily have been overlooked if present in specimens studied previously. 188 Bulletin of Marine Science [19(1)

Dimensions.-Length of body, 15-16 fL; total length, 55-57 fL; depth of body, 30-32 fL; height of midbody, 11-13 fL; height of anterior cingular list, 29-33 fL; height of posterior cingular list, 15-18 fL.

Histioneis panda Kofoid & Michener Figs. 31-33 Histioneis panda Kofoid & Michener, 1911: 298.-Kofoid & Skogsberg, 1928: 694, figs. 85: 1; 95:9.-Wood, 1963b: 7, fig. 18. The body is sausage shaped in lateral view, higher dorsally, expanded in the dorsal half, and somewhat concave on the posterior side of the ventral half. The anterior cingular list is elongated, reticulate, flares distally, and has a dextroventral notch. The posterior cingular list has large lateral pouches; it is flared anteriorly. The cross-rib is undulating. The frill is irregularly reticulated in the anterior half, the reticulation extending ventrally. The left sulcal list is somewhat irregular along the ventral edge; it is irregularly reticulated except for the hyaline area between R2 and R;{. The irregularly reticulated lateral fin is nearly triangular in ventral view. A younger specimen was much less reticulated in the right frill and had only a few branches from the main ribs in the posterior portion of the left sulcal list. R2 and R~join to form a semicircle. Three specimens were seen and measured.

Dimensions.-Length of body, 21 fL; total length, 93-99 }I-; depth of body, 44-49 fL; height of lowest part of body, 9-11 fL; height of anterior cingular list, 45-50 fL; height of posterior cingular list, 31-35 fL·

Histioneis paulseni Kofoid Figs. 34-36 Histioneis paulseni Kofoid, 1907: 204, pI. 15, fig. 94.-Kofoid & Skogsberg, 1928: 650, fig. 95:8; pI. 20, figs. 1, 2.-Wood, 1963a: ]8, fig. 58. The body is subrotund in lateral view and laterally compressed. The epitheca is inclined ventroposteriorly. The anterior cingular list flares, is supported by relatively strong ribs, has a ventral notch, and is not elongated. The posterior cingular list is hyaline, except for the supporting ribs, and slightly gibbous behind the cross-rib. The frill is very difficult to see, quite narrow, and flaring. The left sulcal list is narrow anteriorly and has an undulating ventral margin. R2 is straight and short; RB is weakly sigmoid to nearly straight and varies in position. The "riblets" between R2 and R3 mentioned by Kofoid & Skogsberg (1928: 651), vary in number and simplicity. A small triangular list may be present behind Ra. The four specimens seen are smaIler and more rotund than the type-specimen. 1969] Norris: Thecal Morphology of Ornithocercus magnificus 189

31 32 33

45)..J

34 35 36 37

25u . 25lJ 251-1 . 201-1 FIGURES 31-37. 31, Histioneis panda, right lateral view; 32, H. panda, right ventral view of same specimen; 33, H. panda, right lateral view of another specimen (note the immature lists of the right side); 34, H. paulseni, right lateral view; 35, H. paulseni, left lateral view of another specimen; 36, H. paulseni (?), right lateral view (the body is much the same as in the other two sl?ecimens, but the left sulcal list is quite different); 37, H. variabilis, right lateral vIew.

Dimensions.-Length of body, 26-27 fL; total length, 35-48 fL; depth of body, 25-27 fL; height of anterior cingular list, 12-13.5 p.; height of posterior cingular list, 10-13 fL. Histioneis variabilis Schiller Fig. 37 Histioneis variabilis Schiller, 1933: 231, fig. 223a-d.-Rampi, 1947: 10, fig. 15.-Halim, 1960: 196, pI. 2, fig. 17.-Wood, 1963a: 20, fig. 65. 190 Bulletin of Marine Science [19(1 )

80·

30'

26'

26" - 23 o 20 o 18 o 4 24" - o 16 o 14o

22"

60·

FIGURE 38. Stations where microplankton collections were made. Chart by O. D. Baker.

The body is cherry shaped, although slightly compressed laterally. The anterior cingular list is elongated, flared in the distal third, and has one cross-rib and a few longitudinal ribs anteriorly. The posterior cingular list has a low frill supported by a few longitudinal ribs. Lateral lobes, extending beyond the body, are present. Posteroventrally, each lobe has a lateral rib. The left sulcal list is slightly convex ventrally and rounded posteriorly.

R2 and Ra are both ventral. Anterior R2 is sigmoid and appears to extend beyond the margin of the list; posterior R2 is curved posteriorly to unite with R~.There are a few ventral branches. Ra appears to be forked so as to join the body as two separate ribs. A hyaline lateral fin is present near R~.This specimen is smaller than those previously recorded.

Dimensions.-Length of body, 18 p,; total length, 40 p,; depth of body, 19 p,; height of anterior cingular list, 21p,; height of posterior cingular list, 16 p,. DISCUSSION As expected, the number and general arrangement of thecal plates of Ornithocercus magnificus are the same as in O. thurni, which was studied by Nie (1943). There are differences, especially in structural detail, some of which are considered to be a matter of interpretation. 1969J Norris: Thecal Morphology of Ornithocercus magnificus 191

The most obvious difference is the apparent number of pores present in specific plates. Both dorsal epithecal plates and the posterior sulcal plate have one longitudinal row of pores, not two rows as in O. thurni. The right sulcal plate has only one pore, not two. These differences are at- tributed to the difference in size of the plates in the two species. The two dorsal cingular plates differ in the arrangement of pores in the two sFecies. O. magnificus has distinct rows, near the anterior and posterior margins. Although there are distinct rows in Nie's figure of these plates, he described them as not arranged in rows. As found in previous work on the tribe Dinophysoidae, the pore plate and the anterior and left sulcal plates in O. magnificus are without pores. More significant is the presence of an apical pore. This character has been seen in all species in the Dinophysoidae studied, with the exception of O. thurni. Its presence in O. magnificus implies that it escaped detec- tion in O. thurni. Though it may be a matter of interpretation, it is difficult to accept the lack of a notch in the right dorsal hypothecal plate as described by Nie. There definitely is such a notch in this plate in O. magnificus, a character in agreement with the work of Tai & Skogsberg (1934). It is significant that the anterior sulcal plate appears to be in contact with the flagellar pore. This too, is in contrast to the previous description of O. thurni. Only one sulcal plate (posterior) in O. thurni was noted as having a projection directed into the cell. Two sulcal plates (posterior and left) in the species studied by Tai & Skogsberg have such a projection. In O. magnificus, each of the four sulcal plates has a process directed into the cell. In one instance (Fig. 6), a very fine continuation from a spine near the dorsoanterior corner of the left dorsal cingular plate was observed. It appears to follow the contour of the anterior cingular list, and is assumed to have been attached to that list in situ. A corresponding spine was seen in the right dorsal cingular plate of the same specimen (Fig. 5). These apparently occur only in more mature individuals. The significance of these features must be left to conjecture, pending further detailed studies. Discussion of these or similar features is found in Tai & Skogsberg (1934).

ACKNOWLEDGMENTS The author is grateful to the Graduate College and the Department of Oceanography, Texas A&M University, for support received through the course of this study. I am indebted to many individuals for their help during the period of research and writing of this paper. Special thanks are due: Dr. Leo Berner, Jr., for critical comments and suggestions; and Pro- 192 Bulletin of Marine Science [19(1) fessor Enrique Balech, Director of Hydro Biological Station, Puerto Que- quen, Argentina, for his encouragement and his comments on my identi- fications.

SUMARIO MORFOLOGIA DE LA TECA DE Ornithocercus magnificus (DINOFLAGELLATA) CON ApUNTES SOBRE ESPECIES CON ELLA RELACIONADAS

Se ha hecho un analisis de las placas tecales de Ornithocercus magnificus. El numero y la disposicion general de estas placas son iguales a las de O. thurni, especie estrechamente relacionada con ella, previamente estudiada. Se dan a conocer algunas diferencias en detalles estructurales. Entre las especies de la familia Ornithocercidae que son raras 0 que previa mente no han sido reportadas en el Golfo de Mexico, estan incluidas seis del genera Ornithocercus, ocho del genera Histioneis y una del genera Parahistioneis. Se dan descripciones generales de las especies de Histioneis que difieren de ejemplares previamente descritos.

LITERATURE CITED BALECH, ENRIQUE 1962. Tintinnoinea y dinoflagellata del Pacifico. Revta. Mus. Argent. Cienc. Nat. Bernardino Rivadavia lnst. Nac. Invest. Cienc. Nat., Cienc. zoo!., 7(1): 1-253, 26 pIs. 1967. Dinoflagellates and tintinnids in the northeastern Gulf of Mexico. Bull. Mar. Sci., 17(2): 280-298. CURL, HERBERT, JR. 1959. The phytoplankton of Apalachee Bay and the northeastern Gulf of Mexico. Pub!. lnst. Mar. Sci. Univ. Texas, 6: 277-320. DAVIS, CHARLES C. 1954. Phytoplankton of the Gulf of Mexico. Fishery Bul!. Fish. Wildl. Servo U. S., 55: 163-169. GRAHAM, HERBERT W. 1942. Studies in the morphology, taxonomy, and ecology of the Peridiniales. Pub!. Carnegie lnst., No. 542, 129 pp. 1954. Dinoflagellates of the Gulf of Mexico. Fishery Bull. Fish. Wild!. Servo U. S., 55: 223-226. HALlM, YOUSSEF 1960. Etude quantitative et qualitative du cycle ecologique des dinoflagelles dans les eaux de Villefranche-sur-mer. Ann. lnst. Oceanogr., Monaco, Nouv. Ser., 38(2): 123-232, 5 pIs. KING, JOSEPH E. 1950. Preliminary report of the plankton of the west coast of Florida. Quart. J. Fla. Acad. Sci., 12(2): 109-137. KOFOID, CHARLES A. 1907. Reports on the scientific results of the expedition to the eastern tropical Pacific, in charge of Alexander Agassiz, by the U. S. Fish Commission Steamer "Albatross," from October, 1904, to March, 1905, Lieut. Commander L. M. Garrett, U.S.N., Commanding. IX. New Species of Dinoflagellates. Bull. Mus. Camp. Zoo!. Harv., 50: 161-207,18 pls. 1969] Norris: Thecal Morphology of Ornithocercus magnificus 193

KOFOID, C. A. AND JOSEPHINE R. MICHENER 1911. Reports on the scientific results of the expedition to the eastern tropical Pacific, in charge of Alexander Agassiz, by the U. S. Fish Commission Steamer "Albatross," from October, 1904, to March, 1905, Lieut. Commander L. M. Garrett, U.S.N., Commanding. XXII. New genera and species of dinoflagellates. Bull. Mus. Camp. Zool. Barv., 54: 265-302. KOFOID, C. A. AND T. SKOGSBERG 1928. The Dinoflagellata: the Dinophysoidae. Mem. Mus. Compo Zool. Barv., 51: 1-766, 31 pIs. MURRAY, GEORGE AND F. G. WHITTING 1899. New Peridiniaceae from the Atlantic. Trans. Linn. Soc. London, Bot. Ser. 2, 5: 321-342, pIs. 27-33. Nm, DASHU 1943. Dinoflagellata of the Bainan Region. VII. On the thecal morphology of Ornithocercus thurni (Schmidt) Kofoid et Skogsberg. Sinensia, Nanking, 14; 23-28. NIE, DASHU AND C. C. WANG 1941. Dinoflagellata of the Bainan Region. III. On Metadinophysis sinensis, a new genus and species of Dinophysidae. Sinensia, Nanking, 12; 217-226. RAMPI, LEOPoLDa 1947. Osservazioni sulle Histioneis (Peridinee) raccolte nel Mare Ligure presso Samemo. Bull. Inst. oceanogr. Monaco, No. 920, 16 pp. 1950. Peridiniens rares ou nouveaux pour Ie Pacifique Sud-Equatorial. Bull. Inst. oceanogr. Monaco, No. 974, 12 pp. SCHILLER, J. 1933. Dinoflagellatae. Rabenhorst's Kryptogamenflora, Bd. 10, Abt. 3, Teil 1; 1-617. SIMMONS, ERNEST G. AND WILLIAM B. THOMAS 1962. Phytoplankton of the eastern Mississippi Delta. Publ. Inst. Mar. Sci. Univ. Texas, 8; 269-298. TAl, LI-SUN, AND T. SKOGSBERG 1934. Studies on the Dinophysoidae, marine armored dinoflagellates of Monterey Bay, California. Arch. Protistenk., 82; 380-482, pIs. 11-12. WOOD, E. J. F. 1954. Dinoflagellates in the Australian region. Aust. J. Mar. Freshwat. Res., 5; 171-351. 1963a. Dinoflagellates in the Australian region. II. Recent collections. Tech. Pap. Div. Fish. Oceanogr. C.S.I.R.O. Aust., No. 14, 55 pp. 1963b. Dinoflagellates in the Australian region. III. Further collections. Tech. Pap. Div. Fish. Oceanogr. C.S.I.R.O. Aust., No. 17, 20 pp.

&lt;I&gt;Ornithocercus Magnificus&lt;/I&gt;

<I>Ornithocercus Magnificus</I>