352 



SYNOPSIS OF THE VERTEBRATE FAUNA OF THE PUEKCO SERIES. 



HEMITHL^EUS Cope. 

 Amer. Naturalisl, 1883, p. 833. 



But two species of this genus care known to me, one of which has not been 

 described. This is the H. apiculcdus, and it shows such strong tendencies to Ani- 

 sonchns that it is possible that the two genera will have to be combined. Both 

 species of Ilemithlfens have an internal cusjJ on the second superior premolar, as in 

 Anisonehus. The position of the A. haldioini remains uncertain. 



Fijr. 11. 



Fitr. 12. 



Fig. H. nrnillhJinm kowalevs/danun, last, five suiierior niolare, * natural size. Fig. 13. Protor/onia pucrccnsu, supe- 



riiir (Icnlitidii, loss foiirtli prciiicilar. i. natural size. 



IlF,ivriTin,,mis Anoui.ATrs Cope. Aiu'noneJius iipiriihitiis Cope; Tertiary Vcrtebrala, 1885, PI. XXV c, fig. 7. 



The mandibles of this species have been in my possession for a considerable 

 time, and I have regarded them as indicating a small variety of the Anisonclius sec- 

 torins. But the discovery of the superior dental series shows that the species is 

 quite distinct, and belongs between that animal and the Ilemiihhcus koivalevsMmius 

 in its characters. 



As in the t3'])e of Hemithlreus there are an anterior and a posterior cingula of 

 the superioi- molars. The posterioi* cingulum is produced a little further inwards 

 than the anterior, but on the first true molar its border does not project further in- 

 wards than the internal angle of the crown. In the second molar it projects a little 

 further, while in the third it projects so distinctly beyond the third cusp as to resem- 

 ble the condition seen in Anisonehus. The anterior edge of the cingulum does not 

 form a cusp, however, in either tooth, and for this reason I retain the species in the 

 genus rieniithl.TBus. External cingulum distinct. The internal cusps of the first and 

 second premolars are intermediate in form between the concentric type of A. sectorins 

 and the conic form of A. coniferui^. Tiie transverse diameter of the first premolar is 

 a little greater than tiiat of a true molar, while the crown of the third premolar is 

 subtriangular in section. The infra{)rl)il;il foramen issues above the second pre- 

 molar. 



In the infci'ior Iruc niol.irs flic lifth cusp is pres(>nt, and is connected by ridge with 



