276 PROCEEDINGS OF THE ACADEMY OP [1886. 



214) refers to remains of Hydrochoerus, which he refers to two 

 species, one as H. affine Capybarae, not diflferent from the living 

 Capybara, and another which he calls H. sidcidens^ of a size inter- 

 mediate to the latter and the Tapir, and having the incisors 

 deeply grooved in front. He remarks the former differs in having 

 the incisors smooth in front as in the living species, which sajung 

 is obscure, for in the living Capybara the incisors are con- 

 spicuously grooved in front. 



Prof. Owen (Yoyage of the Beagle 110), speaks of a decom- 

 posed molar tooth of Hydrochoerus, found with remains of Mega- 

 therium, Toxodon, etc., by Mr. Darwin at Bahia Blanca, S. A. 

 He remarks that the fossil differs from the corresponding tooth 

 of the Capybara, in the greater relative breadth of the component 

 laminse. 



Prof. Gervais (Rech. Mara. Fos. de I'Amerique Meredionale, 

 1855, 12), describes remains of Hj'drochoerus, found with those 

 of Megatherium, Toxodon, etc., at Tarija, Bolivia. They con- 

 sisted of portions of upper jaws, which are regarded as pertaining 

 to a species but little different in size and in the form of the teeth 

 from the recent Capybara. They are referred to the E. affinis 

 Capybarae of Dr. Lund. A specimen of a maxilla with the last 

 two molar teeth, figured in Plate xiii, fig. 3, of the work, indicates 

 a more robust animal than the living Capybara, and the last 

 molar tooth is composed of fourteen plates, a greater number 

 than exists in the recent animal. In four skulls of the latter he 

 found the last upper molar to have twelve plates, while in the fossil 

 described by Gervais there are fourteen plates. Couiparative 

 measurements of the latter fossil with the recent animal are as 

 follows : 



Capybara. Tarija fossil. 



Last molar, fore and aft diameter, 33 to 34 mm. 50 mm. 

 Last molar, transverse diameter, 12 to 13 " 20 " 

 Penultimate molar, fore and aft, 9 to 10 " 14 " 



He thought it probable that the remains of Hydrochoerus.^ 

 referred by Lund and Gervais to H. affinis Capybarse, and those 

 mentioned by Owen, as above noted, probably also belong to the 

 species he had named H. robustus. He formerly described some 

 remains of Hydrochoerus, which were found in association with 

 those of 3Iegatheriu7n, etc., in the Ashley Phosphate Beds of 

 South Carolina (Post-pleiocene Fossils of South Carolina, 18G0, 

 112, pi. xxi, figs. 3-6). These consist- of teeth, which agree in 

 size with those of the recent Capybara, and were referred to a 

 probably extinct species, with the name of H. ^sopi. 



The most interesting fossils of the collection are those of Toxo- 

 don, as being evidence of the former existence of this remarkable 

 animal in North America. The best preserved and best marked 

 specimens consist of a nearl}^ complete lower molar tooth, and 

 two portions of a lower incisor. These in their form and size best 



