54 

 HELALETES, Marsh. 



Am. Journ. Sc. and Arts, 1872, p. 218. 



Additional material enables us to give further character- 

 istics of this genus, which may be thus denned : Mammals, 

 allied to Lophiodon, having a third lobe to the last lower molar, 

 short symphysis, and with the teeth of the lower jaw form- 

 ing a continuous series. Astragalus has narrow, oblique 

 condyles. Dental formula : I.g, C. , Pm., ^, M. g. 



Synopsis of Species. 



A. Teeth small ; a small tubercle on the outer margin, be- 



tween the cusps of last upper molar H. hoops. 



B. Teeth much larger and proportionately broader ; no 



tubercle on last upper molar H. latidens. 



HELALETES LATIDENS, sp. nov. 



Loiver Jaw. The ramus is stout, and resembles in gen- 

 eral form that of Hyrachyus, but the alveolar border is 

 straighter than in that genus ; the ascending portion forms 

 a right angle with the horizontal portion, and the masseteric 

 fossa is deep. The symphysis is comparatively short, and 

 there is complete bony union between the rami, which do not 

 diverge so much as in Hyrachyus. As in that genus, there 

 are several small mental foramina beneath the premolar 

 series. The dental series forms a nearly continuous line, the 

 only diastema being a very short one between the first and 

 second premolars. The incisors have compressed fangs, and 

 are arranged in a slight curve. The canine is small and sub- 

 circular at base. The premolars also are small ; they some- 

 what resemble those of Hyrachyus in shape, but are smaller, 

 and have the posterior lobe not so well developed. The 

 first is implanted by a single fang, the others by two. The 

 molars (except the last) consist of two pyramidal lobes, 

 which form transverse cutting-crests, as in Tapir us and 

 Hyrachyus. The basal ridge is shown on the anterior and 

 internal sides only. Externally the lobes meet at their bases, 

 inclosing the valley on that side. The last molar is by far 

 the longest of the series, and consists of three lobes, of which 

 the anterior is the largest, and the posterior the smallest. 



