{anterop 

 transve 



SYNOPSIS OF THE ^■E1:TEB1IATE FAUNA OF THE rUEKCG SEKIES. 325 



the median tubercle as large as the external, thus developing a liocl. There is a low- 

 basal ciuoiiliim on all the true molars on the external side, but none on the inner side. 

 The external side of" the heel of tlie i). m. i has a low ciniiuhiin. The enamel is 

 minutely rugose, but is worn nearly smooth in old examples. 



Measurements of Ramus. M- 



Total length . . .loO 



Length of dental series 088 



" moiar " 073 



" " true molar series 037 



p.m.! 0013 



anteroposterior 0105 



I'erse 008 



f anteroposterior 0135 



Diameters m. li { .._ 



[^ transverse OO'J 



Depth ramus at m. i 028 



m. iii 028 



" " from summit of condyle 036 



Width of coronoid process at anterior base 015 



The mandible from which the above description is taken is that of a diil'erent 

 individual whose ci'anial characters are given on a previous page. 

 All the specimens are from the Lower Puerco beds. 



MiOCLiESDS PENTACUS sp. nov. 



Represented by mandibular rami of seven individuals, which display all the molar 

 teeth excejDt the fourth, which is represented by its alveolus. The character of these 

 teeth is a good deal like that of the Protogonia jniercensis, but the absence of superior 

 molars prevents my learning whether the species is one of the Phenaeodontiche or 

 not. If it is, it belongs to a genus of that fltmily hitherto undescribed, since the 

 first premolar is absolutely simple, or without internal cusp. This fact prevents my 

 reference of the species to the genus Chriacus, to which the details of the structure 

 of the true molars have much resemblance. My reference of this species to Mio- 

 clajnus is therefore purely provisional. The veiy robust form of the lii-st premolar 

 resembles that of the Ilaploconus eiituconus rather than that of any species of Mio- 

 clajnus. 



The inferior molars are robust and Phcnacodus-like, but the lifth cusp is well 

 developed in all of them, forming an anterior tiiangle. The three cusps of this tri- 

 angle are only connected at their bases. The heel is wide and supports a large exter- 

 nal marginal cusp and a curved raised margin behind and within, which is nolehed 

 at two points so as to produce two nai-row areas on wear. On the third true molar 

 these are represented by distinct but rather small tubercles. The second true molar 



