1890.] NATURAL SCIENCES OF PHILADELPHIA. 53 



One marked feature of this fauna is that, while related to others 

 of the lower Eocene, only one of the genera and none of the species 

 have been found elsewhere. The order best represented is the I n- 

 s e c t i V r a with at least four genera, then the C r eo d o n t a with 

 three genera, the ]M e s o d o n t a or L e m u r o i d e a, and the M u 1- 

 t i t u 1) e r c u 1 a t a. The last is a distinctively Mesozoic order and 

 embraces in this horizon the s\ng\e genus Neop lag ianlax, the surviv- 

 or of an ancient and widely spread family. Leaving this exceptional 

 type out of consideration, the following are the general characteristics 

 of the Cernaysian mammals: 1. The teeth are tritubercular^ and 

 in only one genus (Pleiiraspidotherium) is the hypocone of the superior 

 molars fully developed ; the intermediate tubercles (para- and mela 

 Connies) so characteristic of the Wasatch mammals, are not gener- 

 ally well developed. In the inferior molars, the primitive triangle 

 is, in most species, broken by the loss of the paraconid. 2. The 

 brain is small ('82a p. 333, Ardocyon, Pleuraspidotherinm), with 

 large olfactory lobes, narrow hemispheres leaving the optic lobes ex- 

 posed and short transversely extended cerebellum. 3. The skull 

 (excepting in the Lemuroidea) has a deep sagittal crest and broad, 

 low occiput, with slender widely-arching zygomata, and the anterior 

 nares small and terminal in position. 4. The feet are plantiyrade 

 (again possibly excepting the lemurs). One feature of great inter- 

 est to which Dr. Lemoine called the writer's attention is the invari- 

 able presence of the a s t r a g a 1 a r foramen (see fig. 5, o/.) ; this 

 is observed also in all Puerco astragali. The femur has a third 

 trochanter and the humerus usually has the entepicondvlar fora- 

 men. 



1 The following is a table of the nomenclature which I have proposed for the 

 tooth cusps equivalent to that employed by Gaudry in the " Euchainements du 

 Monde Aninia/" p.oo. (See 1, p. 1072.) These terms express the homologies 

 which exist between the upper and lower molar cusps, of all the known mam- 

 malia excepting those with muitituberculate molars. 



Abbr. Molaires stipeneitres. Abbr. 



I, denticule interne du premier lobe protocone, pr. 



E, " externe " " " paracone, pa. 



e, " " " second " metacone, me. 



M, " median " premier " protoconule, pi. 



ni, " '■ " second " metaconule, ml. 



i, " interne " " " hypocone, 



Molaires inferieiires. 



E, denticule externe du premier lobe protoconid, pi^ 



(denticule interne ant^rieure) paraconid, pa^ 



I, " " du premier " metaconid, me<> 



c, " externe du second " hypoconid, hy<J 



i. " interne " " " entoconid, en'' 



