PAL^EOSYOPS LEIDY, AND ITS ALLIED. 
279 
B. Ascending ranms of mandible very long, 
a. Size inedinin. 
Inf. molars stout and broad, posterior tubercle a lobe. P. longirostris. 
PALaCOSYOPS PALUDOSUS. 
(P. major Leidy) (Limnohyud robushis Marsh.) 
The description of some scattered molars of this species by Leidy' in 1870 is the 
fii’st indication we have of the existence of this subfamily. Later, in his “ Extinct 
Vertebra ta of the West, ” he added largely to his above preliminary notices, and 
compared the teeth of this species to his P. minor, but did not give a full descrip- 
tion of tlie dentition. Leidy’s later material Achicli he referred to this species, 
largely consisted of lower molars,” the material for the superior dentition being 
rejjresented by scattered molars oidy. Scott and Osborn^ in their report de- 
sci’ibed the canines and incisors, and referred to Leidy lor further particulars as to 
the dentition in this species. Cope also follows the above authors and refers to 
Leidy’s description. As this, in some respects, is the most important species of this 
sul:)family, and a large collection of the teeth being in the Princeton Museum, 
I shall give the descriptions of its dentition in detail and point out especially its 
specific character ; I shall also dwell largely upon the variable characters of the denti- 
tion exhibited by this species. 
General Description of Dentition . — There are two very fine specimens of 
portions of skulls of this species in the collection ; one containing both the upper 
and lower series of molars (No. 10.009). The other specimen is a part of the facial 
region of oJie side complete (No. 10,282 b), A\diich has the incisors and molars 
in a very good state of preservation. These two skulls are very interesting, as after 
a close study of their characters I can find no specific ditference between them ; bnt 
they exhibit certain variations in their dentition, especially in relation to the size of 
the teeth and the unAvrinkled condition of the enamel. These differences I consider 
as a sexual variation, and in describing the dentition of this species, I shall refer 
to the variation shown by the male and female respectively. An attempt to de- 
scribe the dentition in both sexes of a fossil animal is, I think, quite a novelty, as 
the investigator in this branch of science sees very little mentioned about sexual dif- 
ferences..'* I imagine in a great many cases we may have different species described 
under the same genus, whereas really they may be only sexual differences of the 
same species. 
The superior incisors in this species are arranged in a semi-circle, the in- 
crease in size being from Avithin ontAA'ards. The external incisor is separated from 
the canine by a diastema. The incisors in this species differ from those of Telmato- 
iProc. Acad, of Xat. Scien. Phil., 1870, page 113. 
^Extinct Vertebrate Fauna, etc., plate 24, figs. 1 and 2. 
®E. M. Museum Bulletin of Princeton College, 1877, page 28. 
^Marsh’s Monograph of the Dinocerata. 
