PURBECK FORMATIONS. 63 



the socket of the last molar. A portion of the bony palate and the beginning of the zygo- 

 matic or malar process of the maxillary are preserved ; the outer side is exposed. 



The molars in place are worn down nearly to the cingulum, which extends along the 

 outer side of the base of the crown ; its division into the three compressed lobes is just 

 traceable ; the grooves on the inner side of the crown indicate the action of the lobes 

 of the lower molars. In size the molars in the present specimen are rather less than those 

 of the smaller sized example of Triconodon mordax (PI. Ill, fig. 9). 



Triconodon, sp. ind. Plate IV, figs. 6, 6 a. 



The subject of PI. IV, fig. 6, nat. size, with the three molars magnified 3 diam. at a, 

 is part of a right mandibular ramus, with the three molars and sockets of the premolars. 

 The lower portion of the ramus, as well as the fore and hind ends, are mutilated, and 

 the specimen is chiefly valuable as showing the characters of the inner side of the true 

 molars. 



There is a progressive increase in antero-posterior extent from the first {m \) to the 

 third [m 3) molars ; the cones show an inclination backward, not observable in PI. Ill, 

 figs. 7, 8, and 9. Moreover, the cingulum is not tuberculate or crenate, as in PI. Ill, 

 figs. 9 and 11, and it extends into and developes a larger posterior basal prominence or 

 talon in each molar. 



The correspondence in general size or extent of the series of three molars is very 

 close between the present specimens (PL IV, fig. 6) and the subject of PI. Ill, fig. 9. 

 But the above-defined differences in form and proportions lead me strongly to incline 

 to see in the specimen here described the indication of a distinct species of Triconodon. 



Triconodon, sj3. ind. Plate III, fig. 21. 



The subject of PI. Ill, fig. 21, is the fore part of a right mandibular ramus, with the 

 first and fourth premolars, part of the first true molar, and the crushed socket of a 

 canine, nat. size. The molar (;;^ 1) has a compressed antero-posteriorly extended crown 

 of the triconodont type, but with the mid cone only entire; the front one, as in fig. 12) 

 was obviously lower, the hind one more nearly equal to the mid one. The last premolar 

 consists of a main cone with a fore and hind basal talon, the apex of the cone rising 

 higher than that of the mid cone of the contiguous molar. The small anterior premolar 

 (jo 1) is too mutilated for characterising. All the premolars and the molar were inserted, 

 each by two fangs. 



The teeth agree in size with those in Triconodon ferox (figs. 12 and 13). The ramus 

 of the jaw beneath the first and second premolar is less deep and more convex externally 



