1881.] YlL [Cope. 



CORYPHODON SIMUS Cope. 



A broken mandible and maxillary bone, with several teeth represent 

 this small species in the Big-Horn collection. 



CORYPHODON ELEPHANTOPUS CopC. 



Portions of the dentition of both jaws, including the last molar teeth 

 of two individuals, prove that this species inhabited Wyoming in the early 

 Eocene period. One of the individuals, represented only by -the last 

 molars of both jaws, is a little smaller than the typical specimen of which 

 an entire cranium is figured in Capt. "Wheeler's report (4to, 1877, PL 

 LI-III), while a second specimen, which includes the entire superior 

 molar series, is a little larger than the same. 



This species is characterized by ]the obliquity of the edge of the posterior 

 crest of the posterior superior molar backwards away from a transverse 

 line ; and by the slope of the external side of this crest. In other words 

 the inner half of the posterior crest nearly forms a V, like that of the 

 penultimate molar. The posterior edge of the V is present, running out- 

 wards from the inner end of the posterior crest, which thus becomes the 

 apex of the V. The C. eUphantopus thus most nearly approaches the 

 genus Manteodon, af all the species. To accommodate the obliquity of 

 the crest the posterior outline of the last upper molar is strongly angulate, 

 giving a sub-triangular outline. The heel of the last inferior molar is 

 insignificant. 



CORYPHODON REPANDUS, Sp. UOV. 



This large species is known from the posterior portions of the dentition 

 of both jaws, with an entire symphysis. 



The last superior molars are intermediate in outline between the regular 

 oval of tlie C. radians, and the sub-triangular form of the C. eUphantopus. 

 The peculiarities of the species are seen in the posterior crest. The two 

 lobes of which this is composed, do not form a continuous line as in C. 

 latipes and G. siinus, but form an angle with each other as In C. anax. 

 The anterior lobe is compressed, and its long axis is nearly that of the jaw.; 

 the second lobe leaves it at a right-angle, but curves backwards as it ex- 

 tends inwards, giving a concave exteroposterior border. There is no ridge 

 descending outwards from the inner extremity of the crest, to form a V, 

 as in C. eUphantopus. But the posterior basal cingulum extends to 

 the external side of the tooth, which is not the case in any other species 

 known to me excepting the C. marginatus. The anterior cusp is closely 

 joined to the external elevation of the anterior first cingulum as in C. anax ; 

 a character which separates it from all other species. A strong trace of a 

 cingulum passes round the in'ner base of the crown. No external cingulum. 

 The first true molar does not ditfer materially from that of other species. 

 It is considerably smaller than the last. The apex of the premaxillary 

 bone with the second incisor and alveolus of the first, is preserved. The 

 bone is rather short. The crown of the incisor is regularly convex ex- 



PROC. AMER. PHILOS. SOC. XX. 111. V. PRIKTED MARCH 16, 1882. 



