0. C. Marsh — -New Miocene Mammal. 



409 



Art. XLVIII. — A New Miocene Mammal ; by 

 O. C. Marsh. 



Various remains in the Yale Museum seem to indicate a 

 new ungulate mammal, apparently allied to Hyojiotamus. 

 The specimens, although distinctive, were not found together, 

 and their relation to each other cannot now be determined. 

 A very perfect last upper molar, which may be taken as the 

 type, is shown natural size in the accompanying figures. Its 

 crown is composed of the same main elements as in the corre- 

 sponding tooth of Ilyopotamus, but all the five cusps are much 

 less elevated. In addition, the basal ridge of the outer margin 

 is swollen into two high pointed cusps, making seven in all, 

 and this has suggested the generic name. 



Upper molar of HexAacodon curtus, Marsh. 

 b, outer, view ; c, front view. 



Natural size, a, seen from below; 



Of the outer cusps, or buttresses, the anterior one is the larger, 

 and is situated well forward and partly outside of the main 

 body of the crown. The antero-median cusp is well developed, 

 triangular in outline, and situated somewhat in advance of the 

 other two anterior cusps, as shown in figure a. The two inte- 

 rior cones are connected near their inner margins by a low 

 ridge, and their summits are joined by a high outward-curved 

 ridge, which extends nearly to the centre of the crown. The 

 crown itself is very short, considerably shorter than in the 

 molars of Ilyopotamus. 



The animal thus indicated, which may be called Heptacodon 

 curtus, was somewhat larger than a sheep. The known 

 remains are from the upper Miocene of South Dakota. 



Tale University Museum, April 14, 1894. 



