56 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [VolY. 



CAiiNIYORA. 

 HOPLOPHONEUS BRACHYOPS Cope. 



Mach^rodus strigidens Cope. 

 Enhydrocyon stenocephalus, gen. et sp. nov. 



Generic Charaeters. — Dental formula: I. ?; 0. -f 5 Pm. f j M. ^. The 

 superior iwemolars consist of two ordinary and one sectorial; the 

 iirst and second are both compressed, two-rooted, and in the typical 

 species with median lobe of posterior cutting edge. The two true mo- 

 lars are transverse and tubercular. The three inferior premolars are 

 all two-rooted, and with posterior lobe in the two known species. The 

 heel of the sectorial is cutting, as in Temnocyon, and the internal tuber- 

 cle is present. There is at least one inferior tubercular tooth ; speci- 

 mens are injured so as not to display a second. 



In a nearly complete cranium belonging to the typical species of this 

 genus, we observe the shortness of the facial part of the skull as com- 

 pared with the length of the cerebral, and also the constriction of the 

 skull behind the orbits. The zygomatic arches are robust and expanded, 

 and the sagittal crest is high. The auditory bullae are inflated and thia- 

 walled. 



The dentition of this genus refers it to the Ganidce, but the form of the 

 skull resembles that of Futorius vison and Lutra. 



Specific Characters. — The principal cusps of the inferior premolars 

 present cutting edges, as does the median posterior lobe. In both third 

 and fourth there is a small conic heel posteriorly, but an anterior basal 

 tubercle on the fourth only. The sectorial is large and robust, and the 

 heel is short, with an absolutely median cutting edge. The first tuber- 

 cular is longer than wide, and presents a nearly median cusp in front, 

 which is joined to a low one on the internal border of the crown. 



The superior canine has an obtuse cutting edge on the anterior and 

 posterior borders of the inner side. The first (third) superior premolar 

 is near to it, and is rather larrge, displaying a median cutting lobe and 

 low posterior heel. The fourth is similar but larger. The sectorial is 

 much worn in the only specimen where it is preserved; it is rather short, 

 and is widened anteriorly. The first tubercular is large, and has con- 

 siderable transverse extent ; it is a httle wider externally than inter- 

 nally, and has much the form of the corresponding tooth in Canis. The 

 second tubercular is transverse and small, not being much more than 

 half the length of the first, and is situated in contact with it. 



The cranium is remarkable for the anterior position of the orbits, and 

 the associated shortening of the face and lengthening of the parietal 

 region. The orbits look somewhat forwards and very little upwards. The 

 superciliary region is slightly prominent, and there is a prelachrymal 

 concavity. The infraorbital foramen is moderate, and is situated mostly 

 above the posterior part of the fourth premolar. The muzzle is flat 



