614 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxxvi. 



This species, the type of the genus, was founded on a single lower 

 premolar and was later suj)pleniented by portions of jaws of other 

 individuals. The following definition is compiled from descriptions 

 given by Cope and Osborn, which have been verified or corrected by 

 a recent examination of the type-material : 



Dental formula. — i^, c^, pm,, m, ; premolars 1 and 2 wanting; ps 

 vestigial ; pj greatly enlarged, with high compressed crown, which is 

 develojjed into a sharp, serrated cutting blade, which has 12 (14?) 

 parallel oblique ridges on either side; m^ narrow and elongate, with 

 4 internal and 5 external tubercles; vl\-, much shorter and somewhat 

 broader than m^, with 2 inner and 3 outer tubercles. Upper dentition 

 of this species not known. 



Measurements of type. — Diameters of pm^ : anteroposterior, S) 

 mm. ; transverse, 3 mm. ; height, G mm. 



Measurements of neotyye (after Cope). — Length of ramus to last 

 true molar, inclusive, 20.5 mm. Diameters of m^ : anteroposterior, 

 4 mm. ; transverse, 2 nnn. Diameters of m^ ; " anteroposterior, 2.5 

 mm. ; transverse, 2.2 mm. Diameters of pm^ : anteroposterior, 8.5 

 mm. ; transverse, 3 mm. Vertical diameter of pm^ at middle, 4.5 mm. 



PTILODUS TROUESSARTIANUS Cope. 

 Ptilodus ti'oucssartianiis Cope, Amer. Naturalist, XVI, 18S2, p. OSO. 

 7'ype-specimen. — A fourth lower premolar in a fragment of jaw. 

 (No. 3025, Amer. Mns. Nat. Hist. Coll.) Paratypes: Two additional 

 fourth lower premolars of other individuals. 

 Type-locality. — Northern New Mexico. 

 Horizon. — Torre j on formation. 

 The description, as given by Cope, is as follows : 



This specios is represented l»y three of the eharaeUn-istic fourth inferior 

 preniohirs, one of which stands on a part of the ramus, j;iviug its depth. 

 These differ from those of tlie /'. mcdiwvus in their uniformly smaller size and 

 in their stroufjly serrate posterior edi^e. The luunher of lateral edgos |rid.i;es| 

 is 12, as in P. incilurvus. Length of fourth premolar, M. .0055; elevation of 

 same, .0040; depth of ranuis at P.-m. iv, .0057. 



This species is known only from the material described above, and 

 except for its small size is not well characterized. It represents a 

 much smaller species than P. mediaums. 



PTILODUS PLICATUS (Cope). 

 Chirox pUcatus Cope, Proc. Amer. Phil. Soe., XXI, 1SS4, p. 321. 

 Type-specimen. — A series of three upper premolars, p^ to p^. (No. 

 3032, Amer. Mus. Nat. Hist. Coll.) 



Neotype. — The palate portion of the skull, containing the pre- 

 molars and the first true molar of the right side, and premolars 1, 2, 



" Measurements for nii are taken from Cope's figure, Tertiary Vertebrata, 

 Rept. IT. S. Geol. Surv. Terr., 1S84, i)l. xxiiirf, fig. lb. For other measuremeuts, 

 see Cope, Amer. Naturalist, 1S84, p. 694. 



