1883.] 321 



[Cop9. 



cusp has a V-shaped section, because its anterior border is continued as an 

 oblique ridge to the base of the anterior internal cusp. Internal cingula 

 none ; a slight one on the external base of the large anterior external 

 cusp. The heel of the third true molar is well developed, and rises into 

 an acute cusp. That of the fourth premolar is short and flat. The anterior 

 cusp of the same is basal and rudimental. This tooth is not enlarged as is 

 usually the case in the Periptycliidm, and it first here differs from these 

 animals, and agrees with the unguiculate types in that its lateral faces are 

 unequally convex. 



Measurements. M. 



Length of last four molars on base 014 



" " fourth premolar 0035 



Elevation of " " 0038 



Length of second true molar 0031 



Width " " " (greatest) 003 



Length of third " " " 004 



Width " " " " 0028 



Depth of ramus at second true molar 007 



Anisonchtjs cophater, sp. nov. 



A mandibular ramus supporting three molars, two of them true, is all 

 that I have seen of this species. Its proportions are the same as those of 

 the A. aga/petillus, that is, much smaller than the A. gillianus, and the 

 single premolar is much more like that of other species of the genus. The 

 true molars differ from those of the A. agapetillus in two strong characters. 

 First, the internal posterior cusp is inside the rim of the heel of the crown, 

 that is, outside the bordering edge, and is therefore very distinct from the 

 posterior median cusp. It is a sharp cone ; secondly, there is a cingulum 

 extending from this cusp round the internal base of the internal anterior 

 cusp. There is also one at the base of the external anterior cusp, which con- 

 tinues to the heel only on the last inferior molar. The posterior heel is rela- 

 tively wider, and the anterior V relatively more contracted, than in the A. 

 agapetillus. The anterior tubercle is moderately developed at the anterior 

 base of the anterior V. The third or fourth premolar is equilateral, and 

 larger than the true molars. It has a short apiculate heel, and a rudimental 

 anterior basal tubercle. 



Measurements. M. 



!/ anteroposterior 0032 

 horizontal | trang 

 vertical ( antenor 0025 

 I posterior 0013 



C anteroposterior , 0043 



Diameters of P-m. iii or iv -j vertical (restored apex). . . .0040 



(_ transverse 0023 



D. Baldwin, discoverer. 



Chirox plicatus, gen. et sp. nov. 



Char. gen. These are known from three superior molars ; viz : the last 



PROC. AMER. PHILOS. SOC. XXI. 114. 20. PRINTED JANUARY , 1884. 



