SYNOPSIS OF THE VEItTEBRATE FAUNA OF THE PUEKf O SERIES. 347 



CONDYLARTHRA. 



Amon«^ the specimens whicli represent this subordei', some display poitions of 

 the tenii)oniry dentition. I have aheady described this in Periptychus, but have had 

 uo light on that of the other genera. 



A cranium and a separate set of jaws of Haplocomis cornicalatus display the 

 last two temporary molars of the superior series. The third superioi- true molar is 

 just protruding and the two temporary molars in question remain in place considerably 

 worn. The last temporary molar is scarcely distinguishable in all its details from the 

 permanent true molars. The penultimate deciduous premolar closely resembles in 

 form and size the peimanent first premolar, diftering only in the presence of a small 

 anterior basal cusplct. In a lower jaw of the Anisonclms (jillianus the deciduous last 

 inferior pi-emolar is in place with the crown of its successor below it, and in front of 

 the latter is the crown of the penultimate permanent molar. The penultimate 

 deciduous molar is wanting. The last deciduous molar resembles in every respect the 

 first true molar. We have now in this kind of dental succession a state of affairs 

 similar to that which I have described in the creodont genus TriTsodon, and which is 

 probably common to all Creodonta. The last deciduous molar in both jaws resem- 

 bles exactly the true molars. "Were this tooth not shed these animals would be like 

 the Marsupialia in presenting the false appearance of four true molars. 



I have shown that in Ectoconus the deciduous premolars iv and iii have the pat- 

 tern of the permanent true molars (Tert. Vert., PI. XXIX d, fig. 4). The corre- 

 sponding inferior deciduous teeth are also like the true molars, the penultimate with 

 the fifth cusp more anterior in position. 



In the genus Protogonia I have observed that the last deciduous inferior pre- 

 molar is rather more complex in its form than the first ti-ue molar. It possesses three 

 distinct lobes arranged longitudinally, as in the Diplarthra, but the anterior lobe is 

 not so well developed as in those animals. The specialization of this tooth has not 

 progressed so far as it has in the Diplarthra, but a little more tlian in the Peripty- 

 chida^. This character may serve to distinguish the Phenacodontida- lioin tlie Piii|)- 

 tychida'. 



In Periptychus, as I have already shown, tiie last di-ciduous molar is more com- 

 plex than the premolar which succeeds it, but is not quite so much so as a true inolar. 

 It has also a rudiment of the third lobe anteriorly, indicating a -step beyond Ilapiu- 

 conus in antero})osterior enlargement, while it is a step behind in transverse develop- 

 ment. The three genera, considered together, display such a series of progressive 

 modification of the last deciduous premolar, as to convince one of its possession of a 



