Cope.] 4b J [Xov. 15, 



anterior to the tooth more than the long diameter of the latter. The pre- 

 maxlllary suture commences in front of the tooth, and not internal to it, 

 as is represented to be the case in the M. robustus. The section of the 

 crown is a wide oval, the inner side a little more convex than the outer. 

 Dentine thick and equally so all round. Diameters : anteroposterior, 16 

 mm.; transverse, 13 mm. The grinding face is nearly horizontal. As it 

 is quite oblique in the M. harlanii, and on account of the smaller size, I 

 refer this fragment provisionally to the M. renidens. 



Three inferior molars, which correspond in size with the i/. renidens, 

 are provisionally referred to it ; especially as the third presents characters 

 quite distinct from those of the M. harlanii. Tlie first tooth is not pre- 

 served. The second is like the corresponding tooth in the two larger spe- 

 cies. The section is trilobate, the narrowest and most distinct lobe 

 directed posterointernally ; the long axis of the two other lobes, which 

 are less distinct from each other, at 45^ with that of the jaw. The grind- 

 ing surface of the two anterior lobes is directed obliquely forwards, and 

 that of the posterointernal lobe obliquely backwards, tor contact with the 

 second and lliird superior molars. 



The third inferior molar exhibits externally the outlines of a parallelo- 

 gram with rounded angles, in its cross-section, as in the other species, but 

 the inner extremity is different. The internal border is oblique, and not 

 parallel to the external border, owing to the fact that the anterior internal 

 angle is much exterior in position to the posterior internal angle, from 

 which it is separated by a shallow concavity which presents forwards and 

 inwards, as the section of a groove of the shaft, which is wanting in the 

 two larger species. The anterior and posterior faces present each an open 

 shallow median groove. 



The last inferior molar does not differ in form from that of the M. har- 

 lanii and M. robustus. 



Measurements of Inferior Molars. mm. 



( longitudinal 46 



Diameters of m. ii J anteroposterior, 45° 18 



/ transverse, 45° 15 



longitudinal 58 



Diameters of m. iii .^ anteroposterior, 45° 11 



transverse, 45° 19 



longitudinal 60 



Diameters of m. iv ^ anteroposterior 26 



least 7 



transverse. 



greatest, 45° 19 



Mtlodon sulcidens, sp. nov. 



Tliis species is represented by a penultimate inferior molar of a species 

 of the size of the M. harlanii. Accompanying the remains of the two 

 Bpecies are two penultimate superior molars of opposite sides, which I 



