NO. 1449. THE OSTEOLOGY OF SINOPA— MATTHEW. 205 



f I'iig-uients of the skeleton in had preservation and was suhsequently 

 referred hy its descriher to Stt/j)oloj)hus {=Sinoj}a). 



Ciinohyxnodon Filhol is nearl}^ allied to Slnopa and Proviverra., 

 hut may he held as generically distinct from either. The type is a 

 finely preserved skull, and other excellent material illustrates the genus. 



The definitions will he as follows: 



Family Hypenodontida'. Carnassial teeth, M f. 



I. M -^ absent, protocones and inetaeonids absent Hysenodon 



II. "Si '^ transverse. 



A. Cusps massive, protocones and metaconids reduced, carnassials large, anterior 

 molars small, transverse molar small Pterodon 



B. Cusps sharp, protocones and metaconids well developed, transverse molar 

 larger. Molars of more equal size, with broad external cingula. 



1. Paracone and metacone connate on M i -2 , metacone vestigial on M ^^-. 



a. No metaconid on P ^ Proviverra 



b. Metaconid on P a well developed; premolars long 



Tritemnodon, new genus. 



c. Metaconid on P 1 well developed; premolars high Cjinolnjivnodon 



2. Paracone and metacone well separated on M i-s, metacone well de- 

 veloped on M'^ Sinopa 



These genera show the diflferent stages in the development of the 

 highly specialized flesh-cutting teeth of Hydenodon from the compara- 

 tiveh^ primitive opossum-like teeth of Sinopa. Arranged according 

 to cusp development, they stand thus: 



Hysenodon 

 Pterodon 



Cynoliyse.nodon 



Proviverra Tritem,nodon 



^"^^-^ Sinopa 



(cf.) Deltatheritmi 



This is in partial hut not complete correspondence with their known 

 geological occurrence, as follows: 



