A MEMOIR UPON THE GENUS 
320 
the buttresses which are so characteristic of the external V’s in Lambdotherimn. 
The form of tlie molar in P. borealis approaches more closely that of Telmatother- 
ium than of Paleeosyops, being of a nearly square form without very prominent ex- 
ternal buttresses. The external lobes of the molars are moderately high, and traces 
of an external cingulum are present. The protoconule of all the three superior 
molars is large, especially that of molars 2 and 3. There is no metaconule upon 
molar 1. The second and third molars in this specimen are so badly damaged that 
it is impossible to determine the presence of this conule. 
Slight traces of transverse ridges are to be seen in the molars of P. borealis. 
In the first molar these ridges are only slightly developed, whereas in the last 
molar the anterior ridge connecting the paracone with the protoconule is plainly to 
be seen. The last named conule is largely developed. Compared with those of 
Lambdotherium the protoconules and transverse ridges of P. borealis are not 
nearly so strongly developed. The smaller size and the peculiar oblique form of 
the external face of the true molars in Lambdotherium Avill also readily distinguish 
the teeth of that genus from P. borealis. 
The Skeleton. — The parts of the skeleton associated with the dentition of this 
species are very interesting, and the characters of the well preserved lunar 
strongly remind one of those of Limnohyops. This lunar is high and narrow, like 
that of L. laticeps ; its distal part is prolonged, with the lunar-magnum facet nearly 
vertical in position. The hmar-unciform facet is large and deeply concave. The 
characters of the lunar are also closely related to those of Lambdotherium. A well 
preserved distal portion of a radius (= .031 m.) shows this species to have been very 
much smaller than any other of the known members of the genus. 
P,\L.«OSYOPS MEGAKIIINUS. 
I have established this species' upon the characters of a fine skull (No. 10,- 
008) in the Princeton collection. Unfortunately most of the teeth in this speci- 
men are very badly damaged, only portions of one canine and of the last molar 
being intact. 
Dentition. — The fangs of the incisors which are pi-eserved show that these 
teeth are much smaller than those of P. paludosus, and there is oulj' a small 
diastema between the outer incisor and the canine. The canines of P. mcgarhinus 
are peculiar in form ; they are very small, round in section and divei’ge Avidely from 
the skull. The canine aveolus is very prominent and is a strong character in the 
skull of this species. Only the roots of the premolar series are preserved in the 
specimen. They were probably all much smaller than the pi’emolars of P . paludo- 
sus. There is a considei’able difference in the transverse extent of the last pre- 
molar and that of molar 1. The last upper molar is jiartially preserved and shoAvs 
clearly traces of only one internal cone, a character which places Avith certainty the 
generic jjosition ot this sjjecies. This tooth has a Ioav croAvn and rather bi’oad and 
'American Xaturalist, Jan. 1891, page 45. 
