1892.] NATURAL SCIENCES OF PHILADELPHIA. 311 



PEOVIVEERAi Rutimeyer. 



This genus is very similar to Sinopa, differing from it only in the 

 structure of the last upper premolar (Pj) which is as simply con- 

 structed as in Deltatheriuvi and consists of a triangular, trenchant 

 protocone, a large, conical deuterocone, with no trace of either tri- 

 tocone or protostyle. To this European genus may be provisionally 

 referred a species from the Bridger beds, ? P. americamis sp. nov. 

 (Syn. Sinopa rapax Osborn, Scott and Speir non Leidy) which dif- 

 fers from its European congener merely in size, so far as the very 

 imperfect specimen will admit of comparison. The specimen con- 

 sists only of a jaw fragment containing P3 ^"d ^ which may possibly 

 represent a Bridger species of Didelphodus, but the general fades of 

 the tooth agrees better with Proviverra. The dimensions of P4 are: 

 ant. -post, diameter, 7 mm., transverse, 7 mm. 



DIDELPH0DTIS3 Cope. 

 Syn. Deltatheriitni Cope, in part. 



This genus resembles Proviverra in the structure of the teeth, 

 especially of P4, but appears to have lost Pi, giving the formula 

 I| Ct P'I mi. From Sinopa it differs in the simple canine-like 

 shape of £2, the presence of a deuterocone on P3 and of a corre- 

 sponding element on p*, and the less reduction of ^3. An impor- 

 tant difference from both genera consists in the much less pro- 

 nounced development of the posterior cutting crest on the upper 

 molars. The premolars are all notably high and acute. 



One species : D. (Deltatherium) absarokoi Cope. Wasatch. 



PAL^ffiONICTID^. 

 Syn. AmbloctonidcB Cope. 



Superior molars without or with only rudimentary posterior cut- 

 ting ridge; para- and metacones very high and pointed and well 

 separated ; inferior molars with reduced talon and well developed 

 nietaconid ; proto- and paraconids enlarged, flattened and forming 

 an efficient sectorial blade. Face much shortened. 



PAL5:0NICTIS* de Blainville. 



The discovery of this genus by Wortman in the Wasatch beds in 

 1891 is one of very great interest and importance, both geologically 



^ Eocjine Saugethiere, p. 80. 



2 Pal. Rept. of the Princeton Scientific Expedition of 1877, p. 18. 



3 Amer. Naturalist, 1882, p. 463. 

 ^ O.iieographie, Viverra, p. 76. 



