!J'J1 A MEMOIR ON THE EXTINCT 



The upper part of the face is broad, and relatively moderately convex, in D.labiatus, 

 but narrow and strongly arched in D. torquatus. In the direction of the length of the 

 ossa nasi in the latter it is slightly convex, but in the former in the same direction slightly 

 concave. 



The anterior free extremity of the nasal bones in D. labiatus is relatively long and sub- 

 acute; short and convex in D. torquatus. 



The external face of the malar bone below the orbit in the latter species is more de- 

 pressed than in the other, and its infero-extcrnal margin forms an acute ridge, continuous 

 upon the superior maxillary bone, shelving outwards from above, advancing obliquely over 

 the infra-orbitar foramen, and disappearing in a slight prominence in a position corre- 

 sponding to the bottom of the canine alveolus. The face, below this ridge to the alveolar 

 margin, is concave. In D. labiatus the ridge of the maxillary bone, corresponding to the 

 inferior margin of the malar bone, curves much more upwards than in D. torquatus, and 

 ceases a very considerable distance posterior to its termination in the latter species. Be- 

 neath and within this ridge, the face is more deeply and vertically depressed than in D. 

 torquatus. 



The face, just in advance of the orbits, is less nearly vertical in the latter than in D. la- 

 biatus. 



In the lower jaw the most striking difference between the two species is the strong bend 

 inwards of the angle in D. torquatus, and its nearly vertical condition in D. labiatus. 



Remains of extinct species of Dicotylinre are frequent upon the American continent. 



Lund first announced the existence of such remains in the Danske videnskab. Sclskal^ 

 naturvid. Afhandl. volumes 8 and 9, for 1841-2. lie observes they are often found in 

 numerous caves of Brazil, and in the tables accompanying his memoirs enumerates five 

 extinct species of Dicotyles, but does not describe the specimens upon which they are 

 established. 



In Bronn's Index Paloeontologicus, part first, p. 422, is given the name Dicotyles major, 

 Lund, as described by Clausen in the Neues Jahrbuch fur Mineralogie, etc., 1843, but to 

 this work I have not had access. 



In the American Journal of Science for 1848,* Dr. J. L. Le Conte published an account 

 of a collection of mammalian remains found in the lead region of Illinois. Most of the 

 remains are referrible to Dycotylinrc, of which the author proposed three new species and 

 genera: Platygonus compressus, Hyops depressifrons, and Protochoerus prismaticus. The 

 former of these Dr. Le Conte afterwards described in detail in the Memoirs of the Ame- 

 rican Academy of Science and Arts for 1848.t 



Subsequently, in the Proceedings of the Academy of Natural Sciences for 1S52,J the 

 fragments upon which was proposed Hyops depressifrons were referred to the genus Di- 

 cotyles, and a few additional remarks given upon Protochoerus prismaticus.§ 



*New series, vol. v. p. 102 : Notice of five new species ol Fossil Mammalia from Illinois. 

 1 New series, voLiii., p. 257: On Platygonus compressus: ;i new fossil Pachyderm, 

 ; Vol. vi. p. :(. rbid. p. a. 



