1888.] 



NATURAL SCIENCES OF PHILADELPHIA. 



295 



,A 





^ 



U, Ci, Pi, !U,;, ov p^, m^, as given by Lydekker and adopted by the 

 writer. Owen's formula, jh,, 5»g, includes the canine in the pre- 

 molar series. 



PERAMUS. 



We are fortunately able to greatly increase our knowledge of 

 this genus. Upon uncovering the anterior molars of the type speci- 

 men of Leptocladus, an antero-internal cusp came into view, leading 

 to the discovery that the latter genus is identical with Peramus, 

 and still more interesting is the fact that the type specimen 



of Spalacotherium minus, 

 (Owen) presents the much de- 

 ^-x -f sired internal view of the 

 ( Peramus molars. A third 

 '■-''-"^^ specimen confirms the facts 

 derived from tlie second and 

 shows that altogether there 

 are six or, possibly, seven 

 specimens in the British 

 Museum collection which 

 should be referred to this 

 genus, giving us nearly all 

 the characters of the mandib- 

 ular dentition. These are: 



The type, No. 4774i^, also 

 No's, 47744, 47754, 47743. 

 All except the last, portions of 



/'. /e/iu/ros/ns Owen. Outer face of anterior the left mandibular ramus 

 portion of left ramus. Also, Second Molar geen upon the outer face. 

 of Amphilheriuvi Prevoslii Owen, inteinal j>gfgj.j,g(| j^y Owcn tO PeramUS 

 view. Also, Second molar of P. tniniis, i ]„,,+„^i u,, T ^..^1^1-1-.^,. 



'and so adopted bv L/yaeKker 



cnlarCTed from fi". 1 a aliove ; internal vie\\'. , . „„_ , " 



^ , 1 / -A , -A (op. Clt., p. 277.) 



/r, protoconid./^, paraconid, me, metaconid. ■ ^ ' ^ ^ 



/Jj', hypoconid.w^r, mylohyoid groove. Much To which should be added: 



enlarged. No. 47,739. the type of 



Leptocladus dubhis, (Owen, op. cit., p. 58, PI. Ill, fig. 4 ; Os- 

 born, op. cit., p. 289, PI. 9, fig. 10 ; Lydekker, op. cit, p. 291.) 

 A left mandibular ramus seen upon the outer surface. 

 No. 47,751, tlie tyjie of Spalacotherium viinus. (Owen, op. cit., 

 p. 28, PI. I, fig. 39.) A left ramus seen upon the inner 

 face.^ 

 The heel upon the molars of S. minus and the antero-internal 



cusp upon the antepenultimate molar of Leptocladus suggested a 



^ Also possibly, No. 47799, referred by I-ydekker to Spalacolheritint tniiius, 

 op. cit., p, i!04. 



Fig. ]. 



a. Pdrauius {^Spalacoiherium^ minus 



Owen. Internal view of left mandilndar 



ramus. h. P. [Lefloclin/tis] ihihiits Owen. 



External view of left mandibular ramus, c, 



