NATURAL SCIENCES OP PHILADELPHIA. 113 



very numerous and very abundant in species, and seem to exem- 

 plify tlie views of Prof. Cope in a remarkable manner. Take, for 

 instance, the Ortbis family, one of the most common and prolific 

 both in respect to individuals and species. In this family are five 

 or six -well-marked genera, and yet the specific characters, so far 

 as they are discernible in the hard parts, are often quite identi- 

 cal in species of different genera ; and though they have often 

 varied, yet sufficient constancy is maintained to deceive any care- 

 less investigator, and to give the idea of specific identit}-. It is 

 fairly to be inferred from a study of this class of fossils that 

 generic and perhaps higher characters may change very rapidly, 

 "while specific ones are changing but slowly, nor remaining con- 

 stant. 



May 16. 

 Dr. Carson, Yice-President, in the chair. 

 Twentj^-three members present. 



Remains of Ilastodon and Horse in North Carolina. — Prof. 

 Leidy exhibited two photographs, received from Prof. W. C. Kerr, 

 State Geologist of North Carolina, representing some remains of 

 Mastodon americanus found in that State. One of the specimens 

 represented is that of the greater part of the lower jaw of a mature 

 male, retaining both incisor tusks and the last two molar teeth. 

 The latter, with their angular lobes separated hy deep angular 

 and nearly unobstructed valleys, are quite characteristic of the 

 species. The incisors are an inch and three-fourths in diameter. 

 The last molar has four transverse pairs of lobes and a well- 

 developed heel. The penultimate molar has three transverse pairs 

 of lobes. The specimen was obtained from gravel overlj-ing the 

 miocene marl near Goldsboro', Lenoir Co., N. C. An isolated last 

 lower molar of the same species, represented in companj^ with the 

 jaw, was obtained in Pitt Co. 



Prof. Leidy also exhibited a specimen of an upper molar tooth, 

 which Mr. Timothy Conrad had picked up from a pile of miocene 

 marl at Greenville, Pitt Co., N. C. He suspected, from its size 

 and intricacy in the folding of the enamel of the islets at the 

 middle of the triturating surface, that the tooth belonged to the 

 post-pliocene Equus complicatus, and was an accidental occupant 

 of the miocene marl. It may, however, belong to a Hipparion of 

 the miocene period, but the imperfection of the specimen at its 

 inner part prevented its positive generic determination. 



Remains of Extinct Mammals from Wyoming. — Prof. Leidy 

 then directed attention to what he regarded as one of the most 

 remarkable fossils which had yet been discovered in our western 



1871.] 



