350 STNOPSIS OF THE VERTEBRATE EAUNA OF THE PUERCO SERIES. 



of a cranium with both series of superior molar teeth, lacking the anterior two pre- 

 molar crowns. The only reason for associating the last specimen with the two others, 

 is the identity in proportions and dimensions between them, and as the species differ 

 widely in these respects from the others of the genus, the association is justified by 

 our knowledge as far as it goes. 



The dental characters of the upper series are a diminutive of those of the H. 

 entoconus. The internal cusp of the first premolar is a well-developed cone. The 

 fourth or posterior cingular cusp of the true molars is conic, and is almost on the 

 inner side of the thii-d. The anterior cingulum is distinct and reaches the fourth 

 tubercle. The external cingulum of the true molars is very strong, but is reduced 

 to a trace on the first and second premolars. The second external cusp of the last 

 true molar is very rudimental, so that that tooth is narrower than the others, and than 

 in the H. lineatas. There is a ledge at the anterior base of the first premolar. 



The infraorbital foramen issues above the posterior boi-der of the anterior root of 

 the second premolar. The zygomatic ridge of the maxillary originates above the 

 middle of the first true molar. The nasal bones are elongate. 



In the mandibular dentition the first premolar is larger than any of the true 

 molars, and has a well-developed heel. Its section is nearly a half circle in outline, 

 the external face being convex. The true molars have a cingulum on the anterior 

 half of the crown ; the jjremolars none at all. 



McasiiremeiUs. M. 



LengUi of superior dental series (p. lu. iv, estimated) 024 



" " true molars 008 



f anteroposterior 003 



Diameters p. m. i { 



y transverse 005 



f anteroposterior 0025 



Diameters m. ii \ 



I transverse 006 



Width between p. m. ii 010 



" " m. iii 009 



Length posterior four inferior molars 013 



{anteroposterior 00-12 

 transverse 0025 



. ( anteroposterior 0034 



Diameters ni. i 



transverse 0022 



Depth of ramus at m. i Oil 



This, with the Anisonchus agapetillus, is the smallest species of the Condylarthra. 

 It will not be certain until the superior dentition of the latter is discovered, whether 

 it belongs to this genus or the one in which I have provisionally placed it. 



