Fig. 2. Skull, with angular parts of mandible adherent, cervical vertebræ and scapular arch, from below.

Fig. 3. Skull, from above, with cervical vertebræ.

Fig. 4. Anterior two-thirds of mandibular arch, with adherent premaxillary bones, from above.

Fig. 5. Humerus.

PLATE VIII.

Fig. 1. Pariotichus hamatus Cope; two-fifths nat. size; from above. Fig. 2. Do. from the side.

Fig. 3-5. Hypopnous squaliceps Cope; skull nat. size; 3, from side; 4, from above; 5, from below.

Fig. 6. Chilonyx rapidens Cope; left side of skull from behind and below; one-half nat. size.

PLATE IX.

Diplocaulus magnicornis Cope; 4-7ths nat. size.

Fig 1. Cranium, from above.

Fig. 2. Anterior part of palate.

Fig. 3. Postquadrate region, from below.

Fig. 4. Occipital condyles, from below.

LETTERING.

N., Nasal bone: F., Frontal; Pef., Prefrontal; Pof., Postfrontal; P., Parietal; Pmx., Premaxillary; Mc., Maxillary; J., Jugal; Qi., Quadratojugal; St., Supratemporal; Sm., Supramastoid; T., Tabulare; So., Supraoccipital; V., Vomer; Pa., Palatine; Pur., Paroccipital; Ecp., Ectopterygoid; Ot, Otic bones; Asc, Anterior semicircular canal; Pg., Pterygoid; Q, Quadrate; C., Clavicle; Ep., Episternum; H., Humerus; Co., Coracoid; Ic., Intercentrum.

On Some Plistocene Mammalia from Petite Anse, La.

By E. D. Cope.

(Read before the American Philosophical Society, November 15, 1895.)

The remains of extinct Mammalia from Petite Anse, Louisiana, have been the subject of two brief communications to the Academy of Natural Sciences by Prof. Leidy, 1884, p. 22, and of a longer one in the Transactions of the Wagner Free Institute of Science, 1889, p. 33. Mr. H. C. Mercer has published an account of remains of human industry found at the same locality in the American Naturalist for 1895, p. 393. His remarks are based partly on a letter from Dr. Joseph M. Joor, M.D., of New Orleans, who made an exploration of the locality in 1890, and furnished a very full report to Mr. Mercer. The specimens were placed in the Museum of the Tulane University, of New Orleans. Through the kindness of President Johnson, of the University, the specimens were submitted to me, and I give in the following pages the result of my examination. Dr. Joor reports the occurrence of an Equus and Mylodon harlanii (already mentioned by Leidy), and probably some other giant sloths, a small Mastodon and possibly an Elephas. I can confirm these determinations of Dr. Joor, except as to the Elephas, which I have not seen, and about which the doctor was in doubt.

MYLODON HARLANII Owen.

Of this species the collection contains the following teeth: A complete series of superior molars, all separate, the anterior internal lobe of the third, broken off; the second, fourth and fifth of the superior series of the opposite side, all separate; the first, third and fourth of the inferior series, all separate; separate first and third inferior molars.

The positions of the superior molar teeth have been determined by comparison with the corresponding teeth in place of the Mylodon renidens Cope, described below; and with the figures of those of the M. robustus Owen, given by Owen,* Ameghino † and Lydekker.‡ Leidy has already described and figured the inferior molars.§ In his description Leidy remarks that the superior molars are unknown. I am now able to fill this gap in our knowledge, and to point out some conspicuous characters in which this species differs from the M. robustus of Owen. Leidy has described the second superior molar from isolated specimens from Petite Anse, La., and from Missouri, the latter from the type specimens of Harlan's Orycterotherium missuriense,|| supposing them to be first upper

* Memoir on Mylodon robustus Owen, 1842.

Mamm. Foss. Repub. Argent., 1889.

Annales del Museo de la Plata; Paleontologia Argentina, iii, 1894.

Memoir on the Extinct Sloth Tribe of N. America, Smithson. Contrib. to Knowledge, 1853. | Proceeds. Academy Phila., 1885, p. 49, Figs. 3-6.

1895.1

[Cope.

molars. He remarks that these teeth differ so much from the first upper molars of the M. robustus, that it may be necessary to refer the M. harlanii to a genus distinct from the latter, with Harlan's name Orycterotherium. Since, however, the teeth in question are second molars, the difference is not so conspicuous, and generic distinction is not indicated.

The first superior molar is smaller than the others, is more strongly curved, and the section is a wide oval, the inner side much less convex than the external. The second molar is curved slightly backwards and also outwards, and has a rather narrowly oval or subreniform section, since there is a median groove on the inner side, which is more conspicuous in one of the teeth referred to this position than in two others. The anterior and posterior faces are regularly rounded, and show no traces of angulation. The dentine is about equally thick all around. The grinding surface is worn into two oblique surfaces; the anterior longer and steeper, for the first inferior molar; the posterior shorter, for the anterior face of the apex of the second lower molar. The teeth have very much the form and size of that one described by Leidy as representing his Megalonyx dissimilis, but the beveling of the grinding face, and the equal thickness of the dentine on the inner side, show that the species, at least, are distinct.

The third superior molar is bilobed on the interior side, the posterior lobe being rather narrow; and the external outline is rather narrowly rounded, and is not truncate. The posteroexternal face is shallowly grooved and concave. The long axis is very oblique to that of the jaw. This tooth in the M. robustus has the posteroexternal face convex, and the posterointernal lobe is not so narrow; the axis is very oblique. In the M. renidens it is more different, having the section reniform with the long axis nearly anteroposterior. The fourth superior molar has also a bilobate outline on the internal side, the posterior lobe more produced than the anterior. The crown is quite narrow anteroposteriorly, and the external outline is narrowly truncate. It is represented as rounded in the M. robustus. It has a greater anteroposterior diameter in the M. renidens, and the anterior face is separated from the rounded posteroexternal by an angle. In both of the North American species the groove of the interior face is deeper than is represented to be the case in the M. robustus. The last superior molar is much like that of M. robustus.

The specific difference which distinguishes the M. harlanii most conspicuously from the M. robustus is then the form of the second superior molar. This tooth is much larger in the former, and has an elongate subreniform section, while in the M. robustus the section is round. The third and fourth superior molars also are rather narrower in anteropos terior diameter in the M. harlanii.

It is unnecessary to describe the inferior molars, as this has been already done by Leidy. The resemblance to those of the M. robustus is quite close.