50 DINOCKRATA. 



The second premolar of this series, representing the third premolar, 

 is considerably larger than the one in front of it, and its crown is less 

 compressed transversely. The anterior and posterior lobes of the crown, 

 especially the former, are here elongated in the transverse ridges, 

 approximating to the V-shaped figure in the corresponding upper 

 premolars. The basal ridge is here on the external face, and curves 

 around behind, so as to enclose the posterior tubercle. 



The last lower premolar is very similar in form and size to the one 

 before it, but is somewhat larger. The basal ridge has a similar position. 



The Lower Molars. 



The first true lower molar is smaller than the last premolar, but is 

 similar in the general form and composition of its crown. It shows a 

 greater degree of Avear than the tooth in front of it, thus indicating that it 

 appeared earlier, and is the first of the true molar series. The inner end 

 of the anterior lobe, or ci'est, has its summit divided by a distinct notch, 

 a trace of which was seen in the corresponding part of the last lower 

 premolar. The basal ridge is distinct on the outer face, and likewise 

 curves around behind the postei'ior lobe. 



The second, or penultimate, lower molar is much lai-ger than the first, 

 and has the transverse ridges much more strongly developed. The 

 anterior one is considerably elevated, and the two do not meet closely 

 on the inner side. The basnl ridge is here distinct on the outer surface, 

 and swells in front into a distinct ridge, and behind into a broader crest, 

 or heel. 



The last lower molar in Dinoceras is much the largest of the series. 

 The anterior crest is nearly straight transversely. The posterior crest is 

 inclined inward and forwai-d, the two meeting on the inner face, forming a 

 distinct V-shaped pattern. The posterior lobe, or heel, is here largely 

 developed, and more distinctly separated by a deep valley, from the two 

 crests just described. 



The position and general form of the lower molar teeth in Dinoceras 

 laticeps is shown in Plates XII and XIII. 



