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On the Characters of Some Paleozoic Fishes

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On the Characters of Some Paleozoic Fishes — ON THE CHARACTERS OF SOME PALEOZOIC FISHES. r.v E. D. Cope. (^VVitb Plates xxviii— xxvin. > I. On a new l^LAS.MOBRANCII FROM Till: I'EUMIAX. Styptobasis kniglitiana Cope. Oen. et sp. i:ov. Fi<j. 1. Char. Gen : The single tooth which represeuts this geuus has an eh)ngate compressed crown with two opi)osite simple cutting edges. Botli faces are convex, the one much more so than the other. No hit- eral processes or denticles. The most remarkable peculiarity is in the root; it is very small, having no greater width than the crown, and contracting from the base of the crowu to a truncate termination but a little distance removed from the former. The crown of the tooth resembles that of an Oxyrhina, but the root is totally different. In this respect it resembles a Dendrodus. Char. Specif.: Cutting edges of tooth continued to base of crown. Surface of crown everywhere smooth. Truncate extremity of root a crescent with obliquely truncate horns with coarsely rugose surface. "Where the cutting edges are vertical their surface is below the more convex side of the crown. The root has a lateral edge at each side, which extends obliquely from below the cutting edge to the lateral angle of the truncate base, and is marked ofit" from the base of the crown by a constriction. The base of the crown is openly emarginate by an angle of this constriction. On each side of this emargination the surface is transversely wrinkled. On the same side the root is similarly wrinkled ; on the opposite side the wrinkling is less distinctly transverse. Measiiremeiih. Millinieter.s. Total elevation of tooth 025 '20 Elevatiou of crowu ' Diameters of crowu al)Ovo base : Longitudinal Oil Transverse 005 Diameter of root: Longitudinal 012 Transverse 0C6 If this species be a Cladodont shark, which is quite po.ssible, it agrees with Lambdodus St. .1. and W. in its single simple crown, but that Proceediuga Xatioual AIuscuiu, Vol. XIV—Xo. 866. 447 — — 448 CHARACTERS OF PALEOZOIC FISHES COPE. genus has a widely exijanded horizontal root, thus differing generically from Styptobasis. The IStyptohafiis hniglitiana was found by Mr. Wilbur C. Knight (to whom I dedicate the species with much pleasure), in what he determines as the Permian formation in eastern Nebraska. It was a large shark of carnivorous habits, and its presence indicates the existence of a marine fauna whose remains have not yet been discovered. 11. On New Ichthyodorulites. Hybodiis regularis, sp. nov. Fig. 2. Dorsal spine elongate, gently curved to the apex from the middle. Anterior border rounded, posterior rather broadly truncate, the latter fissured to two-fifths the length of the spine froui the base, and two and two-thirds times as far from the base as the commencement of the an- terior sculpture. Tlie sculpture of the sides descends to opposite the middle of the posterior fissure. Thus the naked inserted portion of the spinels relatively short, and the sculptured portion is long. The latter is also nearly plane. The sculptures consist of longitudinal ribs, which are similar on the front and sides of the spine. Their interspaces or grooves are as wide as the ridges on the front and the anterior half of the spine, but they become narrower on the posterior half, while the ridges are scarcely narrower. The latter are everywhere regular, and do not inosculate, but run out successively toward the extremity on the posterior side. Eight ridges may be counted on the side at the middle of the length and thirteen near the base. Bottoms of the grooves smooth. There is a wide smooth band of surface on each side of the series of teeth, which is separated by an obtuse angle from the lateral face. The teeth are small, acute, and directed downward. They form two approximated rows, the teeth of one row alternating with those of the other. ^ Measurements. Millimeters. Total length (10 millimeters added for apex) 'iUO Length of smooth base in front 48 Length of posterior fissure 129 Diameters at middle of tissure Anteroposterior 2:5 Transverse 14 Diameter (anteroposterior) at middle of length 2'.\ Between apices of teeth of one row 10 The fine specimen on which this species is based was obtained by Jacob Boll from a soft Mesozoic limestone in Baylor County, Texas, which is probably of Triassic age. The species approaches most nearly the Hybodus major of Agassiz, from the Muschelkalk. In that species the teeth are stated to be mere tubercles, which is not the case in this species. — """lioK"'] PROCEEDINGS OF THE NATIONAL MUSEUM. 449 Ctenacanthus amblyxiphias, sp. nov. Fif^. :5. 8piiie eloni^ah^, but little curved, moderately compressed; the pos- terior face with a Hat median plane bounded by a shallow jjroove on each side. The ridges are wider than their interspaces, and they jjradu- ally become smaller posteriorly, So as to be half the diameter of the an- terior ribs. The anterior border consists of a single rib of twice the diameter of the largest lateral ribs. Its front surfa<;e is smooth ; the sides are marked with shallow grooves directed downward, and the border is serrate with subacute tubercles, which point backward. The tubercles of the ribs are closely placed and vary from round to trans- verse in shape, and have a tinely grooved surface. The line of the pos- terior hooks is tlush with the sides of the spine. They are small, decurved, and subacute. The apex of the spine is wanting, so I can not give its length with cer- tainty. It was probably about lOi inches. Measurements: Length of fragment, 100 millimeters; length of base presented (at front), 42 milli- meters; diameters at middle, anteroposterior, 28 millimeters; trans- verse, 17 millimeters; transverse diameter of spine 140 millimeters, from base of fore surface 11 millimeters. The Permian forinatiou of Texas; W. F. Cummins. III. On the Cranial Structure of Macropetaliciithys. The typical specimen of the Macropetalichthi/s rapheidolabis Owen remains one of the best for the elucidation of the type of fishes which it represents, although it is very imi)erfect. It has the advantage of having lost most of the surface of the cranial ossiticatiou, so that its true stru(;ture is the more easily determined. The cavities of the (•ranium are occupied by the Corniferous limestone, which formation is its proper horizon, and one of the orbits contains a characteristic brachioi»odous mollusc. The extremity of the muzzle is broken away oblicpiely, and the (?) maxillary region of the right; side is lost. The matrix has been si)lit from the inferior surface so as to show much of the structure of the latter. The orbits are much in advance of the line dividing the sui)erior head- shield transversely into equal halves. There are no distinct indications of tlu> existence of hyomandibular supports of a lower jaw. There are unsymmetrical transverse sections of hollow rods, which Ibrm area*, im- mediately behind the position of the orbit on the inferior fractured sur- face of the specimen. The fractured surfaces are suboval, and have ditVerent directions of their long axes, owing probably to ditferent directions of pressure. This they would be liable to from the extreme tenuity of their walls. It is probable that this genus had a lower Jaw. As to the ui)per Jaw, this was probably present also, but whether it l)elongs to the palatopterygoid ar(;li or to the maxiUary can not bo rroc. N. 31. 01 20 450 CHARACTERS OF PALEOZOIC FISHES COPE. stated. Its presence is iudieated by tlie longitudinal transversely concave inferior surface of the element called jugal below. This articular surface might have supported some form of tooth, but as no such have been found associated with the rather abundant remains of Macropetalichthys, it is more probable that a distinct element was attached to this surface. As is well known, the superior surface of the head-shield is divided into symmetrical tracts by well-marked lines. These areas have been regarded as the osseous cranial elements, and have been named by Newberry in correspondence with those of higher vertebrata.* The lines referred to, however, are not sutures, but tubes which belong to the lateral line system; and they traverse the centers of the true bony elements instead of bounding them. They join at the centers of some of the elements, and in such cases mark the points of origin of the osseous radii, whose direction they follow. The direction of these tubes is as follows in the present species, and approximately in all the other members of the genus: In the first place there is a frontal lyra, whose branches are parallel for a distance in front of the orbits (as far as the specimen is preserved), and which begin to converge at a point a little in front of the anterior border of the orbit. They join on the middle line about half an orbit's diameter behind the line connecting the posterior borders of the same. From this point they diverge at an angle a little greater than 90 degrees to a [)oint immediately behind the superior border of the orbit, and nearly two orbits' diameter pos- terior to the latter. From this point two lines diverge, one toward the externo-posterior angle of the skull, the other downwards and forwards at an angle a little over 00 degrees from the other branch. The lines are all perfectly straight except those of the lyra, which are bent just in front of the anterior border of the orbits. That these lines represent tubes is readily seen where they are broken across.
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