TULANE STUDIES IN GEOLOGY AND PALEONTOLOGY
Volume 19, Number 4 December 15, 1986
MYTILIDAE (MOLLUSCA: BIVALVIA) FROM THE CHIPOLA FORMATION LOWER MIOCENE, FLORIDA ' HAROLD E. VOKES TULANE UNIVERSITY
CONTENTS Page I. ABSTRACT ...... 159 II. INTRODUCTION ...... 159 III. SYSTEMATIC PALEONTOLOGY 160 IV. LOCALITY DATA . 172 v. LITERATURE CITED 173
ILLUSTRATIONS PLATE 1. 163 PLATE 2. 167 TABLE 1 160
I. ABSTRACT This general preference of most mytiloid The bivalve family Mytilidae, previously forms for shallow-water and intertidal known from the Chipola Formation by hard-bottom environments where dead only a few, mostly fragmentary specimens shells tend to be destroyed by wave action, referable to three species, proves to be rel has resulted in their being relatively rare atively widely distributed throughout the elements in the fossil faunas, with Crenella type area of the formation, being most being apparently the most widely distri abundant in localities where coral is also buted genus. Thus, it is of considerable in present. terest to find in the Tulane University col In this pape r, ten species in eight genera lections from the type area of the Lower are reported from the formation. Included Miocene Chipola formation of northern are three new species and one new sub Florida, ten species referable to eight gen species. era, including each of the four recognized subfamilies (Table 1). In contrast, prior to this report, Dall II. INTRODUCTION (1898b, p. 797) listed only "Modiolus (Bot Species of the family Mytilidae exhibit a ula) cinnamomeus Lamarck" [ ~ Botula preference for intertidal and shallow fusca (Gmelin)] and (p. 806) "a single bro water e nvironments, including: (a) rocky ken valve," identified as "Modiolaria sp. areas, permitting byssal attachment indet." L= Musculus !Ryenella) lateralis (Mytilinae); or burrow ing into rocks, corals praelateralis n. subsp.]. At the same lime, or larger she lls (Gregariella, Botula, most however, he described Modiolus !Brachy Lithophaga); or (b) mud flats for burrowing dontes) grammatus var. curtulus (p. 794) (Modiolinae). The principal exception to and Crenella miniscula (p. 8031 from the these preferences is afforded by the lower bed at Alum Bluff on the species of the genus Crenella, which are Apalachicola River, which contains a most commonly found on muddy silt or fauna that appears to be equivalent to that sand bottoms. Living specimens have been of the uppermost beds of the Chipola For taken from depths down to 460 meters in mation on the Chipola River. Gardner the Pacific Ocean (Bernard, 1983, p. 20) (1926, p. 60) reported the occurrence of and what obviously were dead valves have Crenella in the beds at the McClelland been reported from depths as great as Farm on the Chipola River and from Ten 2,290 fathoms [ = 4,076 meters] (Clarke, mile Creek. Tulane University collections 1962, p. 58). contain more than 700 specimens of C. 159 160 Tulane Studies in Geology and Paleontology Vol. 19 miniscula from 52 of our 57 Chipola thin shells to the point that they are seldom localities. found well-preserved in the fossil record. The generic name Perna usually has III. SYSTEMATIC PALEONTOLOGY been cited as having been proposed by Re Superfamily MYTILACEA Rafinesque, tzius in 1788, but as was noted by A. E . 1815 Ellis in his request to the International Family MYTILIDAE Rafinesque, 1815 Commission on Zoological Nomenclature Subfamily MYTILINAE Rafinesque, 1815 concerning the genus Unio (see Opinion Genus PERNA "Retzius." 495. 1957), "This genus was established in a Philipsson. 1788 [ICZN Op. 495] thesis by Philipsson, working under his master Retzius at the University of Lund. Perna ··Retzius" PHILIPSSON 1788. Disert. By the law or custom then obtaining the Hisl. Nat. Nova Testae. Genera. p. 20. Chlm·omyn MbRCH. 1853. Cat. Conch. Yoldi. pL professor was treated as the author of all 2. p. 52. papers which a student under him de ? Mytiloconcha CONRAD, 1862. Acad. Nat. Sci. fended. For this reason the . names in Phila., Proc., v. 14. p. 290 Las Myti/iconcha, p. this thesis have been attributed . . to Re 579]. tzius. It is clear, however, from the title Type species, by subsequent designation, page that Philipsson was the real author of Soot-Ryen, 1955: Perna m.agellanica "Retzius'' this Disse1·tatio and that the name Unio is ( Mya perna Linnaeus. 1758). Recent. Straits of therefore correctly attributable to him and Magellan (Type locality. fide Sool-Ryen, 1955, not to Retzius." p. 30). north to Venezuela {Rios. 1975. p. 197); South Africa from Namibia to Mozambique (Kil burn and Rippey. 1982. p. 159). PERNACRAURAH. E. Vokes, n. sp. Plate I, Figures 1-3 Discussion: Species referable to the genus Perna may be recognized by their Description: Shell of medium size, mytiliform, dysodont hinge, consisting of one or two with obliquely elongated, moderately convex small denticles close to the beak, by their valves marked by a rounded umbonal ridge paralleling the anterior margin; umbones r·ela pitted resilial ridge below the ligament. tively small, terminaL pointed; posterior margin and by their margaritaceous shell struc slightly convex, almost straight along the length ture. The latter tends to weaken the rather of the ligament, then sharply and subangulately
TABLE I. DISTRIBUTION OF MYTILOID SPECIES IN THE CHIPOLA FORMATION
Number of localities with mytiloid specimens 21 19 15 55 MYTILINAE Penta cTaura n. sp. 6 0 10 16 Brachidontes curtulus (Dall) 5 0 15 20 CRENELLINAE Crenella miniscula Dall 19 10 15 52 Musculus (Planimodiola) disinJ1atus n. sp. 9 0 10 19 M. (Ryenella) lateralis praelateralis n. subsp. 15 14 14 43 Gregariella arcafonna n. sp. 2 3 2 7 LITHOPHAGINAE Lithophaga antillarum (Orbigny) 0 3 4 L. !Diberus) bisulcata (Orbigny) 2 4 7 MODIOLINAE Modiolus ducatelii Conrad 5 2 6 13 M. sp. (immature ducatelii ?) 6 6 10 22 Botula fusca (Gmelin) . 1 I 3 No.4 Mytilidae oflhe Clupoln F'ormaiion Iii! curved llltO a relatively s traight po~tero-\·t·ntr,11 Thl' numlwr ol 'IL'l'th'" 111 tlH• hmgt.~ n d slope that gradually rounds into the \'l'ntral t•nd \ ant>s gn' County, Flor·ida l "t I"\ lO' ~"rctn h '(II I J It 1 1 Pcucttype B: USNM -107801: length t !inl'omplt.· J, ulltlfl t! 1 Ill'- tlo1 't"tt•t· 50.4 mm, width en. 26.5 mm. dianwlt-r rldt Tht· ! t (' U" lldill(' 1!/IU dt•rl\-~d valve) 17.6 mm; locality TC 10-ll-1. F·u·lt·v Creek. Calhoun County. F' londa >'rom tht· (,n·t>k t.' tn "Kr<.~L n 1 H. dlllnf! hriftlt• or h!t· l 1~ .-~pplit i 111 ,diu: ton Tnsofar as the \\TJU•r 1~. Discussion: \() tlw fr.n 1iJt· J"dtL rt ·: tl fc II c~kt aware this is the first species of true Perna to be reported from the fo ssil faunas of thl' eastern United States. The name has bevn Ccr HRAC!!J[)():\ H S "" \H 1 used in the past, however. in the sense of 1-s H'rtlt mttes S\\ <\ \" " \ 1~ 0, rn \I .. H Perna Bruguiere ( 1789. p. 13: lso91W1Hon p. )HI Solander in Lightfoot. 1786 1or of H. and A. h ICIJ 11 o111es. '-1w til X·lll ( 1{\ I~ ' l.ool. Sm ... ot oJ 1 1 c v I J~. Adams (1857, p. 515. as Pernn Adanson. <1 Hrtll l1 11 1o tiPs \( \Sc. ' 'i4j \I)J \1 lot pre~Linnaean name; Jlr1ocliolus La· dt•X lTtl(\ p. ) Hrw/1 ,, . marckl. Sw<~! Woodring (1973, p. 522 1 noted that ca,;t \"JI f Pt' l' \ Ill lll t 1\.l)I.J.Wln Sl' 1 "fl(J from the Culebra Formation of Pm1ama, L. n 1r ._ 1-\ I non I t. r K R which he identified as Mytilus ccuwWH'Hsis nodul n: et ~: 1t1 t.'i It l u rotsson.lvicLali Ferreirct and Cunha lfl.l~l. d!l ••. lj~IH. h oct. E.n 1. Yuc p. 22, pl. 2. figs. Ia. b; described from tlw t,· I\ 1· Ull Umbones very small, subacute, almost but not Figu.1·ed specimen: USNM 407802; maximum quite terminal. Radials along the posterior and length 7.0 mm, height 4.0 mm, right valve; loc ventral margins coarse. heavily corrugated by ality TU 548, Chipola River, Calhoun County, the incrementals. tending to bifurcate toward Florida. the outer margin, not far from 15 in number. Figured specimen: USNM 407803; maximum those upon the anterior slope almost twice that length 6.0 mm, height 3.6 mm, left valve; loc number and consequently much finer and more ality TU 548, Chipola River, Calhoun County, crowded and not dichotomous. Ligament Florida. groove moderately deep. Hinge edentulous. Ad Discussion: Dall (1898b) described cuT ductor scar obscure. Inner margins crenate in tulus as a variety of his new species Mod harmony with the external sculpture, nearly ob solete toward the umbones.·· (Gardner, 1926) iolus (Bmchydont.es) gmmmatus, the type of which came from Ballast Point, Tampa Holotype: USNM 114578. Type locality; USGS 2211, Alum Bluff (lower Bay, Florida. He apparently had but one bed), Liberty County, Florida. valve, which was subsequently figured by PLATE 1 Figures Page 1-3. Pema cTaum H. E. Vokes, n. sp. 160 1. Holotype, USNM 407799 (X 1.5); length 36.4 mm, width 22.1 mm. Locality: TU 459, Chi pol a River. 2. Paratype A, USNM 407800 (X 2); length 13.0 mm, width 6.9 mm. Locality: TU 459, Chi pol a River. 3. Paratype B, USNM 407801 (X 5.5); view of incomplete specimen, showing pitted resilial ridge. Loca lity: TU 1048, Farley Creek. 4, 5. Bmchidontes cuTtulus (Dall). 161 4. Figured specimen, USNM 407802 (X 6); length 7.0 mm, height 4.0 mm. Locality: TU 548, Chipola River. 5. Figured specimen, USNM 407803 (X 6); length 6.0 mm, height 3.6 mm. Locality: TU 548, Chipola River. 6, 7. C,-enella miniscula Dall 164 6. Figured specimen, USNM 407804 (X 13); height 2.9 mm, length 2.0 mm. Locality: TU 70, Tenmile Creek. 7. Figured specimen, USNM 407805 (X 13); height 2.3 mm, length 2.0 mm. Locality: TU 549, Chipola River 8, 9. Musculus (Planimodiola) disinflatus H. E. Vokes, n. sp. 169 Holotype, USNM 407813 (X 6); length 6.6 mm, height 3.4 mm (fig. 8, right valve; fig. 9, left valve). Locality: TU 458, Chipola River. 10, 11. Musculus (Ryenella) lateralis pTaelateTalis H. E. Vokes, n. subsp. 165 10. Holotype, USNM 407806 (X 4); length 10.0 mm, height 6.0 mm. Locality: TU 825, Farley Creek. 11. Paratype, USNM 407807 (X 5); length 5.8 mm, height 4.1 mm. Locality: TU 196, Tenmile Creek. 12, 13. Botula fusca (Gmelin). 172 12. Figured specimen , USNM 407808 (X 3.5); length 10.1 mm, height 8.2 mm. Locality: TU 547, Chipola River. 13. Figured specimen, USNM 407809 (X 2); length 26.0 mm, height 12.8 mm. Locality: TU 1048, Farley Creek. 14, 15. G,-egariella aTcafonna H. E. Vokes, n. sp. 169 Holotype, USNM 407810 (X 5); length 9.9 mm, height 4.9 mm (fig. 14, exter nal view, left valve; fig. 15, hinge and interior, right valve). Locality: TU 1196, Farley Creek. No.4 Mytilidae of the Chipola Formation 163 I .. - \. / 4 8 ., 9 12 10 .'> I 14 15 13 b PLATE 1 164 Tulane Studies in Geology and Paleontology Vol. 19 Gardner (1926, pl. 15, fig. 4). Dall stated: Description: "Shell minute, thin, inflated, "The variety, which more abundant mate elongate ovate, feebly radially striated, the stria rial might show to be a distinct species, is tions apparently diverging from a medial line on the disk; not dichotomous; the beaks smooth; stouter, more triangular, with coarser and inner margins crenulate; valves nearly equilat more nodulous ribs and stronger crenula eral. Alt. 1. 75, lat. 1.25, diam. 1 mm. tions of the margin. Alt. 12, max. lat. 7, "This little shell is rare in the marl and resem diam. 6 mm" (of paired valves). bles in a general way C. divaricara Orbigny, of Gardner (1926, p. 58) recognized cur which it is the precursor, but has fainter tulus as a separate species, stating: "This sculpture and smooth beaks, besides being con ~ form is certainly distinct from the Ballast stantly of smaller size, and is more narrow in Point species which is almost sub-cylindri form than the young of C. divaricata of the same cal in outline and ornamented with a fine length." (Dall, 1898) and delicate radial threading. The lirae in "The smooth prodissoconch can be plainly ob ~ served in these minute forms. The affinities of grarnmatus C~.re double the number of those the species are obviously with the later Tertiary ornamenting M. curtulus, and the fluting or Recent members rather than with the of the inner edges is consequently much Eocene." (Gardner, 1926) finer and more feeble." Holotype: USNM 114624. The type specimen, as figured by Gard Type locality: USGS 2211, Alum Bluff (lower ner, is incomplete with a portion of the beds), Liberty County, Florida. postero-ventral margin broken away, and Figured specimen: USNM 407804; height 2.9 is larger than any of the more 250 speci mm, length 2.0. mm, diameter (left valve) 1.2 mens from the type area of the Chipola mm; locality TU 70 , Tenmile Creek, Calhoun Formation. Our largest specimen, some County, Florida. what similarly incomplete, has a maximum Figured specimen: USNM 407805; height 2.3 length of 10.5 mm. The average number of mm, length 2.0 mm, diameter (right valve) 0.85 mm; locality TU 549, Chipola River, Cal~ coarser ribs is nearer 20 than 15. It also houn County, Florida. should be noted that the hinge area bears a few small and weak teeth, generally two Discussion: Gardner added the first re on the right valve and three on the left. cords of this species from the fauna of the type area of the Chipola Formation, listing Subfamily CRENELLINAE it as rare at USGS locality 3419, "McClel H. and A. Adams, 1857 land Farm 1 mile below Bailey's Ferry" on Genus CRENELLA Brown, 1827 the Chipola River and present at locality 7151, Tenmile Creek, Calhoun County, Crenella BROWN, 1827, Ill. Conch. Great Bri Florida." tain and Ireland, pl. 31, figs. 12~14. Comparison of the more than 700 speci Stalagmium CONRAD, 1833, Foss. Shells Tert. mens from 52 Chipola localities in the pre Formations North Amer., v. 1, no. 4, p. 39 [Oct.]. sent collections with numerous specimens Myoparo LEA, 1833, Contrib. to Geol. p. 73 from the Recent faunas of the Yucatan [Dec.]. Peninsula and the Caribbean Sea area Nuculocardia ORBlGNY, 1842, in DE LA leads the writer to believe that Dall's speci SAGRA, Hist. Fis. Pol. Nat. Isla de Cuba; Pt. men from the lower bed at Alum Bluff may 2, Hist. Nat., v. 5, Moluscos; Atlas, pl. 27, figs. have been rather worn, for the costae on 56-59 [Text, p. 338, 1847; Spanish Ed.]. our specimens are somewhat broader and Type species, by monotypy, Mytilus decus~ stronger than on Crenella divaricata. The satus Montagu, 1808. Pliocene~ Recent, Circum~ shape is almost equally variable in the two boreal. species. The largest specimen in the collection, a CRENELLA MINISCULA Dall Plate 1, Figures 6, 7 worn valve from TU 655, on Tenmile Creek, has a height of3.3 mm, and a length Crenella miniscula DALL, 1898, Wagner Free of2.4 mm. Inst. Sci., Trans., v. 3, pt. 4, p. 803, pl. 35, fig. 22. Crenella miniscula Dall. GARDNER, 1926, U. Genus MUSCULUS Reding, 1798 S. Geol. Surv., Prof. Paper 142~A, p. 60, pl. 15, fig. 9. Musculus RODING, 1798, Mus. Bolten., pt. 2, p. No.4 MytiLidae of the Chipola Fonnation 165 156 [not pr·eoccupied by Musculus Martvn with median arpa smooth except for grmvth 1787. a non-binomial work]. · ' lamellae. and m most specimens delimited from Modiolarilt BECK in ROBERT, i? J 1838, Zoo!. the costate areas by a rounded sulc:us: radial Voy. Recherche en Islande et en GrOnlande. ribs on anterior third and on the ventral half to pl.17. figs. l-4. two-thirds of the posterior area relativeI\' broad ·Lctnistes Humph." SWAINSON, 18-lO. Treat. and 11at-toppecl with slightlv narrower i~ter·-db Malac.. p. 385 [non Montfort. 1810 1Gastr.l. areas marked by lamellosP.nossbar ::> forming a Modiolctrca GRAY, 1840. Synop. Cont. Brit. latticed sculpture, the \'.:idth oftlw inter·-rib o1rea Mus., ed. 42, p. 15llerr. pro Modiolnr·ia.fide decreasmg dorsally on posterior segment until Sherborn, 1928, Index Anim .. p. 4122; how they lose the nossbar sculpture and become ever, Gray, 1847, Proc. Zoo!. Soc. London. v. linear groo\'es bel\veen the narrov.·ed ribs along 15. p. 199. lists type as Modiola trap(>:ina]. the dorsal portion: 15 lo 18 ribs present on an Lcmistaina GRAY. 1847. Zoo!. Soc. London. ter ior segment and -10 to 50 on the pustero-dorsal Proc.. v. 15, p . 199 rn. n. pro "Lanistes Sv.·ain one. Inner margin of valves crenatt• at r b term!· son. 1840; not Montf. ., + Modiolaria 'Beck· nations, median area smooth. Hinge area lack· Loven, 1846;'' Mytilus discors cited as type ing teeth species.] Holotype: L'S!\:\1·Hl'il'l06: lt.•ngth 10.0 mm. twrght Type species, by subsequent de$ignation, 6.0 mm. dianwtt.·r Ot:'ft valve1 cu. 2.H mm. Ir·edale, 1915. Myt"ilus discors L innaeus, 1761. TypP locality: TL H25. Farlev Cret.•k, Cal hot n Recent, C ircumboreal. County, Florida . Pcuntype: C'SI'\~1 -107/:H)'I, k•ngth ;).8 mm. !wight Subgenus RYE NELLA Fleming. 1959 4.1 mm, dtanll't(:r 1rght val\·eJ cu 1.1. mm, locality Tl' 196. femnile Creek, Cdlho1 Ryenella FLEMING, 1959. Royal Soc. r\ew Zea County, Flor (\; land. Trans., v. 87, p. 172. Type specie s, by original designation. Mytilw; DtscHs ...;,o 1 TL. ll~m-lb. p. SO!) I reported impuctus Hermcmn. 1782. Lower· ~1iocene toRe· tlw prvst.•tH'L· L f d 1 1 gle broken \"t.lJ\'t re1 cent. New Zealand. tTsent. lh ·JWCIL' sin :!ar to .'\l1ud Discussion: As pointed out b y Fleming wl tor of the Pliocene (?) to Recent M. Coquilles Foss. Eocene Envi1·. Paris. fasc. 2, latem1is (Say I. p. 159. The species described by Gabb (1881. p. 377. pl. 47, fig. 81 I as Ct·eneUa (Modiolariaj Type species, by original designation. Mod iola sulcata Lamarck, 1805. Middle Eocene, tmnslucida "from the Pliocene Clay Beds Paris Basin, France. between Limon and Moen, Costa Rica" is, as noted by Dall, (1898b, p. 8071 '·a very Discussion: Lamarck (1805, p. 123) de similar species'' to M. lateralis. As com scribed Modiola sulcatct: "Modiola ob pared with our Chipola form, it is relatively longo-spathulata: margine inferiore ar narrower with a straighter ventral margin. cuto, carinato; sulcis transversis diversis. '' The dorsal margin, behind the umbone is In his discussion he noted that ·'Cette es broadly arched trending into the more pece est remarkable par sa forme ... ob sharply rounded postero-ventral end, and longue, presque en forme de spatule," insofar as can be determined from the il with the ornamentation similar to that of lustration, the anterior radials are broader "mytilus discors, Lin .. , The species was and less numerous. not illustrated until 1807 (pl. 17. figs. lla, Musculus praelateralis is, as mentioned 11b). above, represented in the Tulane collec In his description of Planinwdiola tions by more than 190 valves. These come Cossmann noted that the she!ls are ·'ovale from 43 localities extending stratigraphi aplatie, attenuee en avant, elargie en ar: cally from the base to the uppermost beds riere, caract€risee par deux sinuosites qui in the exposed sections: 15 of the localities limitent, sur le contour anterieur, les extre represented are from the banks of the mites de l'aire depourvue de cOtes rayon Chipola River, 14 are from along Tenmile nantes: cette aire est largement develop Creek, west of the river. and 14 are from pee et generalement couverte d'un fin Farley Creek, flowing into the river from treillis de stries rayonnantes et concen the east. triques: bord anterieur et bord ligamen taire bien creneles. ,, Although often considered as being a synonym of Musculus. Planim.odiola is dis Subgenus PLANIMODIOLA Cossmann, tinguished by its more elongate, less in 1887 flated valves with more pronounced and Planimorliola COSSMANN. 1887. Cat. I!lus. sharply rounded anterior extremities. PLATE2 Figures Page 1-4. Lithophaga antiUarum (Orbigny!. 168 1, 2. Figured specimen, USNM 407811 (X ll: length 74 .0 mm, height 23.7 mm (fig. I, lateral view; fig. 2, dorsal view of paired valves). Locality: TU 1048, Farley Creek. 3. Figured specimen, USNM 407812 (X 1.51; incomplete valve. View showing com plex ornament on posterior area of valve. Locality: TU 1048. Farley Creek. 4. Figured specimen (X 1.5); view of posterior area of incomplete valve of Recent specimen; compare with fig . 3. Locality: TU R-109, not·them Panam~. 5, 6. Lithophaga !Diberus) bistdcettCL (Orbigny). 170 5. Figured specimen, USNM 407814 (X 1.51: length 28.6 mm. height 11.7 mm. Locality: TU 1196, Farley Creek. 6. Figured specimen, USNM 407815 (X 1.5): length 24 .0 mm, height 9.2 mm. Locality: TU 1196, Farley Creek . 7. Modiolus ducateUi (Conradi 171 F igured specimen, USNM 407816 (X II: length 90.0 mm. height 59.8 mm. Locality: TV 1196. Fadey Creek . No.4 Mytilidae of the Chipola Formation 167 2 \" '} I• I' I 3 7a sa PLATE 2 168 Tulane Studies in Geology and Paleontology Vol. 19 MuscuLus (PLANI?-.10DIOLA f DISJNFLATUS numerous on the posterior area than in the H. E. Vokes. n. sp. present species. Plate 1, Figures 8, 9 Musculus disinflatus, n . sp., is rep Description: Shell relatively small. elongate resented in the Tulane University collec ovate with greatest height slightly posterior to tions from the Chipola Formation by 79 mid-length of valves: low. prosogyrate umbones valves from 19 localities. The largest valve near anterior end. which is slightly produced has a length of8.1 mm. and broadly rounded: dorsal margin arched, passing int~ the broadly rounded posterior end: Genus GREGARIELLA Monterosato, 1884 ventral margin almost straight with. however, a weak convexity along the margin of the median. Gregariella MONTEROSATO, 1884. Nomen. non-ribbed area: anterior and posterior portions Gen. Spec. Conch. Mediterranee, p. 11. of valve surface radially ribbed with eight to ten Botulina DALL, 1889. U.S. NaU. Mus., Bull. 37. ribs on the anterior area. the more posterior of p. 38. these being broad and flat-topped with slightly Tibialectus IREDALE, 1939, Gt. Barrier Reef Exped., Mol\.1; Sci. Repts., v. 5, no. 6. convexly-bottomed interspaces of approxi 1928-9; mately equal width, both r·ibs and interspaces p. 424. narrowing towards the umbone; the ventral ter Type species. by subsequent designation, mination of the four or live posteriorly convex Crosse. 1885, Modiolus sulcatus Risso, 1826 (nmt inters paces tending to project as rounded areas Lamat"Ck . 1805, nor \819) Modiolus bm·batel crenulating the shell margin: posterior· area with lt~s Cantraine, 1835, = Modiolus opifex Say, 26 to 30 wide, flat-topped ribs separ·ated by rela 1825. Recent, Mediterranean Sea. tively nanow grooves, the more ventrally situa Discussion: This genus of mytiloids is tion costae tending to be almost twice the width of those toward the dorsal portion of the valve known to bore into thick-shelled molluscs surface: median, non-ribbed area forming ap (Carpenter [1857, p. 124] cites borings in proximately two-thirds of the ventral margin. Spondylus calcifer and Murex regius), delimited from the ribbed areas by very shallow rocks (Olsson, 1961, p. 129 ), and corals grooves, its sur{ace marked only by occasional (present collections). growth lamellae: valve margins slightly crenu lated by terminations of ribs except at the post GREGARIELLA A RCA FORMA erior part of the anterior area as noted above: H. E. Vokes, n. sp. ligamenta\ area smooth, but with relatively Plate 1, Figures 14 , 15 strong, tooth-like crenulae immediately below the umbone and on the dorsal slope poster·ior to Desniption: Shell small, convex, modioliform the ligament. almost Area-like in general shape with subter Holotype: USNM 407813; length 6.6. mm. height minal prosogyrate umbones marked by a broad 3.4 mm, diameter (paired valves) 2.4 mm. median sulcus extending to middle of ventral Type locality: TU 458. Chipola River, Cal margin; well-rounded anterior margin passing houn County, Florida. into the ventral one, which is made broadly con cave by the umbonal sulcus: posterior end nar Discussion: The writer is aware of no rowly rounded, almost pointed on ventr·a\ por· similar weakly inflated spatulate species of tion, then trending anteriorly in a slightly con Musculus that has been reported from the vex, almost straight slope to the broadly angled Western Hemisphere faunas, fossil or Re junction with the relatively straight dorsal mar cent. "Modiolus" dalli Glenn in Clark el gin: surface of anter·io t· end with a few micro scopic radial ribs, medial surface smooth up to al., (1904, p. 367, pl. 97, figs. 9. 10) from the posterior side of umbonal sulcus, beyond which Choptank Formation of Maryland appears it is ornamented by fine , rounded radials de* to be most closely approximate in degree scending from the ct·est at posterior side of me of inflation of valves, but differs in being dian inflation and terminating in a descending proportionately higher relative to valve row at edge of median sulcus: posterior· and length, in having a relatively longer, posterio-dorsal surface with stronger divarical straight dorsal margin with subangulate ing radials of'ten nodose when crossed by bend at posterior end, and in apparently t·ounded concentric growth lamellae: inner mar lacking the tooth-like crenulations below gin crenulated by radial ribbing, the crenulae on the anterior end and the posterior portion of the umbone and on the dorsal surface post ventral margin finer and less conspicuous than erior to the ligamenta\ area. Judging from those on posterior area and posterior side of the illustrations it appears that the radial dorsal margin beyond the narrow, linear re costae are narrower and much more silifer, but continuing as weak projections dorsal No.4 Mytilidae of the Chipola Formation 169 to that structur·e; muscle scars not visible. Genus LITHOPHAGA Roding, 1798 Holotype: USNM 407810: length 9.9 mm, height Lilhopltaga RODING, 1798, Mus. Bolten .. pt. 2. 4.9 mm. diameter (paired valves) ca. 4.5 mm. p. 156. Type locality: TU 1196. Farley Creek, Cal Luhophagus MEGERLE. 1811. Ges. Nat. Fr houn County, Florida. Berlin, Mag .. v. 5. p. 69. Lithodonws CUVIER. 1817, Le Regne Animal, Discussion: G·regariella arcaforma is, in \'. 2, p. -171 most respects. similar to G. coaTctata 21.5 mm; locality TU 1048. Farley Creek. Cal LrrHOPHAGA (DIBERUSI BJSULCATA (Orbigny) houn County, Flor·ida. Plate 2, F igures 5, 6 Figured specimen: USNM 407812: length (in Lithodonws bisulcatus ORB IGNY, 1842, in DE complete) 50.7 mm. height (of fragment) 24.4 LA SAGRA. Hist. Fis. Pol. Nat. Isla de Cuba: mm: locality TU 1048. Farley Creek. Calhoun PL 2, Hist. Nat., v. 5, Moluscos: Atlas, pl. 28. County, Fl~rida. figs. 14-16[Texl. p. 352. 1847: Spanish Eel.} Discussion: Lithophaga antillaTu1n may Modiolet appendiclllota PHILIPPI. 1846, Abbild. be distinguished from L. nigra (Orbigny) und Beschreib. Conchyl.. v. 2. p. 150. pl. 1. (1842, pl. 28, figs. 10, 11 ), the only other Re fig. 4. Lithoplwuu (/ppeudt<'rilow Philippi. IVIORCII. cent species of Lithophaga s.s. in the \853. Cat. Conch. Yolcli. pt. 2. p. 56. warmer waters of the western Atlantic Litltodomus bie:rccwatus REEVE. 1857, Conch. Ocean, by its lighter color and by the fact leon., v. 10. Lithodonws. pl. 4. figs. 22a. b. that the posterior area of the valves is Litlwphaga rDiberns) bisulcatn \Orbigny). marked by a pattern of irregularly radiat OALL, 1898, Wagner Free lnst. Sci., Tr·ans .. ing or chevron-shaped lirations or rows of v. 3, pl. 4. p. 801. low nodes, formed by the lateral extension Litlwphar;n (Dibents) bis11lcnta (Orbigny). of the transverse lirae that are present on VOKES and VOKES, 1983. Mesoamet·. Ecol. the more anterior part of the valves. The Inst., Mon. 1 (Mid. Amer. Res. lnst.. Pub\. Chipola specimen here figured (pl. 2, fig. 3) 541. p. 36, pl. 34. fig. 9. Description: ··Lithodomus testa elongata, sub is the most complexly patterned valve that lanceolata. laevigata, epidermide fusca: later·e the present writer has observed, although buccali b1·evi: latere anali elongato, product.o. it is closely approximated by one from the oblique truncat.o. externe ca!careo induto. sub-Recent of the northern coast of racliatim bisulcato: a pice bilamel!ato. Panama (pl. 2, fig. 4 ). ;,Dimension. Longitud 20 mil!im II The fo rm described by Gardner (1926, p. lineas. 60, pl. 15, fig. 10) as Lithophaga o1·yzoides, ..Esta concha es vecina delL. caudigerns de la with the type from the Alum Bluff Group at costa africana, y se distingue por el encos Oak Grove on the Yellow River in tr·amiento esterior formado dos surcos profun Okaloosa County. Florida. and said to be dos que part.en del venice y van ella region anal. donde dejan en meclio una lamina prolongada present also in beds of Chipola age at mucho mas allc) de Ia concha. Se halla en Cuba, Boynton Landing on the Choctawhatchee Ia Jamaica. Ia Martinica. Ia Guadalupe y Santo River, Washington County, although com Domingo.·• (Orbigny. 1847) pared to ·'L. niger D'Orbigny." clearly is Figured specimen: USNM 407814: length 28.G not to be referred to Lithophaga s.s. T he mm, height 11.7 rnm. diameter \left valve) 5.9 essentially modioliform shape w ith nar mm; locality TU 1196. Farley Creek. Calhoun rowed posterior end suggests that, if it is County. Florida. indeed a Lithophaga. it might represent a Figured .specime11: USNM 407815: length 24.0 form similar to L. (Myoforceps) aristata nun, height. 9.2 mm. diameter (\eft valve) 4.1 Dillwyn, in which the secondary posterior mm; locality TU 1196. Farley Cr·eek. Calhoun shelly prolongations have been lost during County, Fl~ricla. . fossilization. Discussion: As noted by Orbigny. it is Lithophaga antillarwn is not common in the external incrustation that forms the the Chipola collections. the specimen here two deep sulcations, which extend frorn figured being the only relatively complete the umbone to the posterior margin. one with paired valves. A second rather Examination of Recent specimens show fragmented pair, plus one almost complete that the incrustration is exceptionally thick valve and numerous fragments. represent in the area between the two sulci and that ing four localities, are present in the its almost. vertical lateral sides serve to em Tulane University collection. phasize the bisulcate appearance. When the incrustation is removed. as in the fossil Subgenus DIBERUS Dall, 1898 specimens where it is not preserved. the Diberus DALL. 1898. Wagner Free Inst. Sci .. sulci on the valve surface are b road and Trans., v. 3. p. 4. p. 799. shallow and not very obvious. Type spectes. by or·iginal designation. Lil.Jwphago rD?benu; ) bisttlcCita is not Lithopltaga plunwla (Hanley. 1843) (as Modioial. rare in the collections from the Chipola Recent. Gulf of California to Peru. Formation. being r·cpr·esentecl by 106 No.4 Mytilidae of the Chipola Formation 171 specimens, of which 14 are paired valves. two "l''s in the name of the species. and These come from seven localities, at all of also earlier for his Venus Ducatelli" t 1838, which corals are present. 11840] pt. 1, p . 8. pl. 4, fig. 21. As far as the The form from Preston Sink, Alachua writer is aware, the earliest emendation to County, Florida, described by Gardner a single "1" was that ofDall, 1893, in his Re (1936, p. 14, pl. 8, figs. 5-7) as Lithophaga publication of the Conrad work where, in cookei from the "Hawthorn formation? of the "Explanation of the P lates" (p. 118- the Alum Bluff group," differs from the 1291, he added to the explanation of plate present species in that the outline of the 4, figure 2 (p. 1181 and plate 28, figure 2ip. holotype mold has the greatest he ight to 1231 , respectively, that the name "should ward the anterior end rather than at a be Ducateli" and "should be written point transverse to the postero-dorsal an Ducatelii." gulation. In 1898b lp. 7931 Dall listed four species of Modiolus from the Tertiary of the east Subfamily MODIOLINAE Keen. 1958 ern United States. as the onlv "valid Genus MODIOLUS Lamarck. 1799 IICZN species belonging to the section ~1odiolus Op. 325] as restricted . . except 1W. tulipus Lam .. Volsella SCOPOLI. 1777 , In tcod. Hist. Nat.. p. which occurs in the later rocks of the "West 397 [suppressed. ICZ N Op. 325]. Indies." The four species were. in addition Modiolus LAMARCK 1799 . ~e m. Soc. Hist. toM. ducatelii: M. siliccttus Dall. 1898b lp. Nat. Paris. v. 1, p. 87. 793. pl. 27, fig 28, where it is identified as Modiola LAMARCK. 180 1. Syst. Anim. sans M. tampaensis Dalll, from the ·'Upper Vertebr.. p. 113. Oligocene silex beds at Ballast Point Perna ''Adanson'' H. and A. ADAMS, 1858. Gen Tampa Bay. Florida" (now considered to Recent Moll., v. 2. p. 515. be of Early Miocene age); 1\1odiolus HI Ewnodiolus IHERING. 1900, Malac. Soc. Lon don, Proc., v. 4. p. 87. ./1atus lTuomey and Holmes! I 1857. p. 33. Type species, by tauionomy, M ytilus mod pl. 14. fig. 31. from the Miocene of New Jer iolus Linnaeus, 1758. Re cent, Ci rcumboreaL sey and Pliocene of South Carolina. and southward to Bay of Biscay and Cape Hatteras M~diola gigcts Wagner in Dall (1898a. p. 10. in Atlantic Ocean and ? to Baja California and pl. 2, fig. 3A, Bl. ?Pliocene, Yorktown. Japan in the Pacific Ocean. Virginia (see Olsson, 1914. p. 1:31. Modiolus ducatelii is represented in the MODIOL US DUCATEJ.II (Conrad , 18401 TulaJH. L nil"t"J".itv Chipol.t l'L lleetion: b.v P late 2, Figu re 7 lll<\11\ v 555. East bank of Chipola River, about 1,000 DALL. W H .. 1898a, 1'\otes on the paleontologi feet above Fourmile Creek (SW 114 Sec. cal publications of Professor William Wagner 29, TIN, R9W). Wagner Free Jnst. Sc1.. T rans. v. 5. p. 7-11. 655. Tenmile Creek, about 0.1 mile down pis. 1-3 (J anuarv. 1898). stream from bridge on Florida H ighway DALL. W. H .. 1898b. Contributions to the Ter 73 (NW 114 Sec. 12, TIN, RlOW). tiary fauna of Florida: Wagner Free Inst. Sc1.. 825. Farley Creek at abandoned mill about 1/4 T ra ns .. \'. 3. pt. 4. p . 571 ~ 947. pis. 23-35 jOc mile west of bridge on Florida Highway tober, 18981. 275 (SW 114 Sec. 21 , TIN, R9W). DALL, W. H .. and JOSEPH STAKLEY 830. Tenmile Creek, at powerline crossing B ROWN. 189..t, Cenozoic Geology along the about one mile west of Chipola River (SE Ap ORBIGNY. A. D .. d', 1842-1845, Moluscos. in family IVIytilidae (Pelecypoclal: Allan llan DE LA SAGRA. Historia fisica, politica y nat eock Pacific Expeditions, v . 20, no. 1. 261 p .. ural de Ia Isla de Cuba, Pt. 2, Historia natural, 10 pis. 78 text figs. v. 5: Atlas. pis. 1-28 ( 1842). text, 376 p . 11845). WHITFIELD. R. P ., J894, Mollusca and Crus RIOS. E. C .. 1975. Brazilian Marine Mollusks tacea of the :\1liocene formations of New J er Iconography. Rio Grande. Brazil. 331 p .. 91 sery: U.S. Geol. Surv., Monograph 24. 193 p .. pis. 24 pis. SAY. THOMAS, 1822, An account of some of the WOODRI!\G, W. P .. 1973, Geology and Paleon marine shells of the United States: Aead. Nat. tology of Canal Zone and adjoining parts or Sci. Phila., Jour .. lser. II v. 2. p. 221-248.257- Panama. Description of' Tertiary Mollusks 276. 302-325. (additions to gastropods. scaphopocls. TUOMEY, :v!ICHAEL. and F. S. HOLMES. pelecypods: Nuculidae to Malleidael: lJ. S. 1857, Pleiocene fossils of South Carolina. Geol. Surv.. Pmf. Paper 306-E. p. i-iv. 453- Charleston. South Carolina. 152 p., 30 pis. 589, pis. 67-82. SOOT-RYEN. TRON, 1955, A r·epo1·t on the AN UNUSUAL DISTORTED SPONDYLUS FROM THE MOIN FORMATION (PLEISTOCENE), COSTA RICA HAROL D E. VOKES TULANE UNIVERSITY A single left valve of a much d istorted lortion appears essentially to have been s pecimen of Spondylus bostrychites Guppy confmed to the anterior side and to have (1867, p. 176) was collected from Tulane tended to till the left valve relative to its locality 953 at Moin Hill, the type locality of original normal position. This is evidenced the Moin Formation (Gabb, 1895, p. 80) by the fact that the rugose increments considered to be of early Pleistocene age progressively ove rla p posteriorly around (Akers, 1972, pp. 42-44, fig. 3). the valve margin such that the area of dis The valve under consideration appears torted growth gradually passes from a to have attained essentially a normal adult width of about 32 mm on the anterior side size and ornamentation, with a height of to being essentially absent just below the 115 mm, a width of 107.3 mm, and a d iame posterior end of the hinge area. ter of 36.5 mm. Then the anterior margin That this same distortion affected the began to trend inwards w ith coarsely hinge area is evidence d by t he greater rugose, non-ornamented growth incre width of its anterior portion and by the fact ments accumulating diagonally to margin that the resilia l pit lends to develop a slight an increasingly smaller valve opening. posteriorly trending curve in its later Prior to the onset of distortion the inne r stages. margin had a width of about 100 mm; this The t·ight valve was not found and its was reduced to 66 mm. T he ma,-ginal dis- condition is unknown. It. seems probable. No.4 Distorted Pleistocene Spondylus 175 however, that it must have developed a LITERATURE CITED similar distortion as the inter-valve margi nal area became progressively narrower. AKERS, W. H., 1972, P lanktonic Foraminifera The reason for this distorted growth is not and Biostratigraphy of some Neogene forma evident; the outer surface of the valve tions, northern Florida and Atlantic Coastal shows no evidence of any d amage. It may Plain: Tulane Stud. Geol. Paleont., v. 9, 139 be that the right valve was the one dam p., 1 map, 4 charts. aged; the fact that the a nterior margin of GABB. W. M., 1895, Informe sobre Ia explora the distorted segment is relatively straight, ci6n de Talamanca verificada durante los aflos de 1873-1874: An. Inst. Fis.-Geogr_ Nac. rathe r th an rounded, and that the entire Costa Rica, v. 5 (18921, p. 67-90. margin is irregularly undulating, not GUPPY, R. J. L., 1867, On the Tertiary fossils of smooth , is indicative of e xtreme distortion the West Indies :Sci. Assoc. Trinidad, v. in that valve also. I, pt. 3. p. 145-176 December 15. 1986 T ext figure 1, Spondylus bost?-ycltites Guppy; height 115.0 mm, width 107.3 mm, diame ter 48.0 mm; locality TU 953, Mo in, Costa R1ca (X H.