260 VERTEBRATE REMAINS, PORT KENNEDY BONE DEPOSIT. 



Mvlohyus tetragonus Cope (PI. XXI, figs. 3, 3a, 3d). [Type No. 108, Mus. Acad. Nat. Sci. Phil.] 



The specimen on which this species is described is an imperfect left mandibular 

 ramus with the corresponding part of the symphyseal region. The fragment 

 includes the canine, three temporary molars, and two true molars. It is so broken 

 that I took from their places the crowns of the last two permanent premolars. 



This jaw displays the long diastema which characterizes M. pennsylvanicus. 

 Of the form of the jaw nothing can be said except that it is rather slender. All 

 posterior to the m T is lost, and the part anterior to that tooth is crushed by com- 

 pression. The canine tooth exhibits a peculiarity which I have not observed in 

 any other peccary. Besides the two wide lateral planes and the narrower posterior 

 plane, which give this tooth a triangular section in the known species, the internal 

 posterior angle is truncated by a fourth plane. This plane extends from the apex 

 to the base of the crown, and faces inward. It widens gradually downward, and is 

 separated from the adjacent faces by distinct angles. Although the tooth is fully 

 protruded its posterior face is not worn, and is slightly concave. 



In the second premolar the four posterior cusps are of about equal size, and are 

 separated by deep fissures. The anterior two are each larger than each of the 

 posterior, and they are separated from each other and from the metaconulid by deep 

 fissures. A minute trace only of paraconulid and none of any other cusps. The 

 larger first premolar has the same number of cusps as the second, and they are dis- 

 posed in the same way. The only material difference is the fact that the metaconu- 

 lid is smaller than the other three cusps of the posterior four with which it is in 

 contact. A minute trace of paraconulid, and none of any other accessory cusps. 

 All the cusps separated by deep fissures. Enamel surfaces smooth. 



The true molars differ from the premolars in that the metaconulid and talon 

 are separated by the mutual contact of the hypoconid and entoconid, and both are 

 smaller than the latter cusps. There is a rudiment of paraconulid as an enlarge- 

 ment of the external posterior basis of the metaconid, which is not cut off by a 

 fissure from the latter. The enamel of all the cusps is plicate. The m T only 

 differs from the m T in its slightly larger size. No external or internal basal cingula ; 

 anterior basal cingulum very slight. 



Measurements. 



mm. 



Length of diastema; 63 



flongitudinal (chord); 36 



Diameters of crown of c T I anteroposterior; 10 



( transverse on posterior face ; 6 



Length of molar series preserved ; 77 



tv , f anteroposterior ; 14 



Diameters, pnw { , L -, n 



' L l \ transverse ; 10 



tv , (anteroposterior; 15 



Diameters, pm T { , L -. 



' l x \ transverse; lo 



-p.. , (anteroposterior; 16 



Diameters, m T < , L -, 



1 J transverse ; lo 



18 



14.5 



