Cope.] 1^4 [.July 16, 



distal portion of tlie right femur of another individual in another mass, 

 and the entire absence of bones or fragments which could be referred to 

 any other animal. In the matrix occurred Turbo pica L., whereby the» 

 postpliocene age of the deposit is to be inferred. 



The molars belong to an animal of the average size of the Castoroides 

 chiensis Foster, and as the epiphysis of the femur is not yet coossified, 

 and the animal is young, I have no doubt, the proportions of the species 

 are quite equal to those of the beforementioned largest of known Ro- 

 dentia. This is confirmed by the proportions of the femora, whose shaft 

 and condyles are larger than those of the 9 Cervus elaphus of four years 

 old, with which I have compared it. What the bulk may have been, is 

 difficult to infer without additional portions of the skeleton, but it is suf- 

 ficiently obvious that this ancient chinchilla exceeded the Virginian 

 deer, and more than equalled the American Black Bear in this respect. 



Three molars are preserved, two of which present four dental columns, 

 and one three. These columns are transverse, the first, which I assume to 

 be anterior, transverse ; the second the longest, the third shortened in- 

 wardly, and slightly curved round the very small fourth, which occu- 

 pies a posterior-external angle of the crown. All are separated by rather 

 thick enamel laminae. The form of the crown of the largest presents 

 two sides of a square anteriorly and externally, the inner side bilobed in 

 correspondence with the two anterior columns ; the posterior strongly 

 convex backwards and outwards. The other, similar molar, diff"ers in the 

 posterior outline being more nearly transverse, and the anterior out- 

 lines being united by a continuous curve. The large portion of the third 

 tooth preserved is perhaps the external ; it is a part of a nearly regular 

 transverse oval. 



The first described molar is strongly curved posteriorly, and its diam- 

 eter narrows regularly to the contracted base ; there is a shallow groove 

 at the junction of the anterior enamel lamina with the inner wall. This 

 groove is much more strongly marked in the second described, but ceases 

 before attaining the contracted extremity. The shank of the tooth is less 

 curved than in the other. The contraction is less gradual than in the 

 first, but is strongly marked at the base, where the pulp cavity is not 

 wider than one of the columns. 



Lines. 



Length anterior face No. 1 (on curve) 143 



Diameter crown (longitudinal) 6. 



" " (transverse) 5.7 



" root (longitudinal) 4. 



Length anterior face No. 2 14.3 



Diameter shank (longitudinal) 6. 



" " (transverse) 5. 



A portion of one of the inferior incisors of some forty-six lines iii length, 

 and another shorter piece, furnish characters of the species and genus. 

 The inner face of the tooth is plane, and at right angles to the anterior ; 

 the outer is rounded obliquely inwards ; the inner face is broad and not 



