PAL^OSYOPS LEIDY, AND ITS ALLIES. 
3<;!» 
of the genus. A striking peculiarity of the first molar is its extremely small size 
as compared with molar 2 ; there is nearly as great a difterence between the trans- 
verse diameters of the first two true molars as there is between pi*emolar 4 and 
molar 1 of P. paludosus, the latter species showing the ditference in size of these 
two teeth more than any other sjoeciesof the genus. Another interesting character 
of the first molar in L. fontiualis is that the primitive triangle is moi-e strongly 
expressed than in any true molar that I have examined in the entire series of 
species. The protocone of molar 1 is very large as compared with the liy|KH‘one and 
is placed further to the inside than the latter. The hypocone is small and placed 
far to the posterior internal angle of the molar, and the whole tooth seems to have 
been in a transition state of development, being in a condition between a premolar 
and a true molar. In the latter the internal cones ai-e of the same size. Tlie second 
superior molar has quite a high crown with flat and broad external lolics; the 
anterior buttress is prolonged, but the median buttress is low and stiungly con- 
stricted off. With the exception of the large size of the anterior buttn'ss the 
structure of molar 2 shows close affinity in form to that of Tehnatolhcrtum. 'flu? 
external lobes of molar 2 hav^e no cingulum, and the V’s are <livided by a faint 
median rib. The internal cones arc subequal in size but do not show the groat 
difterence observed in the first molar. A Avell marked j)rotoct)nule is jjivsent on 
molar 2. Both the internal cones of the last superior molar are well preserved and 
of the same height, thus distinguishing this species from L. lattceps in which then* is 
a great diftei’eiice in the size of the internal cones of the last suj)erior molar. 'I’he 
slight development of transverse ridges on the molars of L. laticcps is wanting in 
this species. The surface of the enamel on the molars of L.fontnialis shows a slight 
tendency to wrinkling, but the teeth are not the least worn. 
Stimmary . — With the exception of the diflerence in size between molars 1 and 
2, I consider that the dentition of this species shows an advance over that of L. 
laticeps. This is proven in the Telmatotheroid characters of its molai-sand also by 
the fact that the internal cones of the last superior molar are ecpial in height ; mon*- 
over the hyj)Ocone of this molar does not exhibit the undifferentiated condition that 
is found in L. laticeps and in some of the transition forms Iretween Limnohyops and 
Palcsosyops. 
Skull . — The skull of L. fontinalis closely resembles in form that of A. Uxticips, 
especially the occipital region. The antero-posterior axis of the skull is considerahly 
extended and the cranium proper is exceedingly broad and depressed. The (h)rsal 
contour of the skull is nearly the exact counterpart of that of L. laticcps, although 
the sagittal region is slightly concave instead ol convex as in the latter s])ecies. 1 lit* 
occipital crest, as in the larger species, is strongly developed for such a small 
animal, and it widely overhangs the supraoccipihd region. The cranial rogion is 
elongate compared with that of the facial portion, the latter lx*ing abbreviate<l. 
Wava/v.— The nasals are broad and short ; their superior surface is Hat and 
distally they do not expand. The lateral portion of the nasals is strongly arched 
