62 PROCEEDINGS OF THE ACADEMY OF [1890. 



^vTriT]n|ir>^^^ IT*?!'?^ arated by well-worn longitudinal valleys. 

 Each of these cones is subcrescentoid as in 

 the upper molars of Tritylodon. The large 

 upper premolar (a) has an indented bor- 

 der and is similar to that found in the max- 



Fig. 6. ilia of Ctenacodon (Marsh) with much 



Neoplagiaulax. a, Prob- ,• ^, • j./e i. 



ably a superior premolar, re- ^^^^^ numerous serrations. It IS difficult 



ferred to N. Marshii. b, N. to form any positive opinion as to the posi- 



eocaenus. Probably a superior ^.j^,^ ^f ^.j^^ ^j^j^.^^ ^^^^.j^ ^gxxx^^ (6). It is 

 premolar, c, A superior true _ . 



molar, the posterior portion of approximately the same size as the above 

 tlie crown partly fractured, premolar, with One elevated row of seven 



All. figures enlarged approxi- . , , , 



mately, ^. marginal tubercles and one depressed row 



of five tubercles. 



BIBLIOGRAPHY. 



4. A. de Lapparent, Traite de Geologic, Paris, 1885. 



5. Archibald Geikie, Text Book of Geology, London, 1882. 



1. Henry F. Osborn, "Evolution of Mammalian Molars to and 



from the Tritubercular Type." American Naturalist, Dec, 

 1888, p. 1067. 



2. Max Schlosser, " Die Affen, Lemuren, Cheiropteren, Insectivo- 



ren, Marsupialier und Caruivoren des Europjiisclien Ter- 

 tiiirs." Wien, 1887. 



