348 MAURICE G. MEHL 
of a supernumerary epipodial, such a bone was probably present to 
fill out the remaining width of the humerus. The radius is remark- 
able for its length, being longer in comparison with its width than in 
any other known American form. Its greatest length is along its 
somewhat thinned outer margin. From here it gradually thickens 
toward the inner side and toward the extremities. The inner face 
is apparently unnotched and shows a close articulation with the 
ulna. The ulna, though not known, must have been pentagonal 
and considerably smaller than the radius. The carpus is repre- 
sented by six bones, three in the proximal and three in the distal 
row. The ulnare has an articular facet on the outer upper surface, 
however, showing the presence of a fourth element in the proximal 
row. The fingers are not greatly elongate and are primitive in 
their relatively small degree of hyperphalangy. The arrange- 
ment of the bones is based partly on the determination of Pro- 
fessor Reed and partly on their relative size and shape. For this 
reason it cannot be said with certainty that the arrangement or 
number is correct. According to this determination there are, 
beyond the metacarpals, two phalanges in the first and six in the 
second finger, with a terminal phalanx missing in each, perhaps. 
There are five phalanges present in the third finger, with the 
fourth missing. In the fourth finger there are six and in the fifth 
five, with number five lacking. In each of the third, fourth, and fifth 
fingers there are probably two or three terminal phalanges missing. 
A brief comparison with other American Jurassic forms will 
serve to bring out the distinctive characters of this species: 
Comparison of the paddle with the outlines of that of Panto- 
saurus striatus Marsh (Fig. tc), taken from a photograph of the 
type specimen made by Dr. Williston, shows a marked difference; 
the radius and ulna in this form are both short, and about equal in 
length and width. 
The description and figure of Megalneusaurus Knight, of which 
M. rex' is the type, shows the difference between these two forms. 
In M. rex the ulnar articular facet of the humerus is convex, the 
radius and ulna are short and of about the same dimensions, a 
radio-ulnar opening is present, and there are but three bones in 
the proximal row of the carpus. , 
t Am. Jour. Sci., V, 378, Fig. 1. 
