— 307 —- 
swimming was that of balancers. In the hind-limb the femur usually 
projects outward nearly at right angles to the body axis, but the knee 
is, in almost all cases, strongly flexed. The pesis very much larger 
than the manus, and the digits increasein length from first to fifth. 
The fact that the digits are so straight and so symmetrically spaced 
in a considerable number of specimens, representing the three known 
species of Proganosaurians, renders it virtually certain that the pes was 
webbed, thus forming an efficient swimming organ. 
The relative lengths of head, neck and trunk in two examples 
measured, are about in the proportion of 18,11 and 29. The largest 
skull in the collection has alength of 110", so that in this specimen 
the length from tip of snout to base of tail was prebably about 450", 
and if the tail bore the same ratio to the length of trunk which obtains 
in Stereosternum, i. e., 15-39, (measured from Woodward, 1897, Pl. 
IV.) the total length from tip of snout to tip of tail was about 1080". 
Most of the specimens known, however, including the largest figu- 
red in the plates, do not exceed three-fourths this size. 
As to the systematic position of the Proganosauria all the chara- 
cters of skull, shoulder-girdle, etc., brought to light in the present 
investigation tend to support H. F. Oshorn’s inclusion of this order 
among the Diapsida. They are acjuatic Diaptosaurians, the ancestry 
of which prohably leads back to some small terrestrial Protorosaurian, 
a form not greatly dissimilar to Peleeohatteria. The view held hy 
Seelev and Boulenger, namely, that these animals have affinity with 
primitive Sauroplterygians, I regard as «{uite untenahle. 
A brief diagnosis of the group may be given as follows: 
Order. PROGANOSAURIA, Baur, 1887. 
Originally defined by Baur as reptiles having five elements 
in the distal row of the tarsus. 
Family. Mesosauride. 
Thesub-order Mesosauria, as defined by Sceley, 1892, p. 
is invalid, since it comprised, in addition to Pro- 
ganosauria, a second division Neusticosauria, (a group 
of primitive Sauropterygians.) I diagnose the family 
as follows: 
Small aquatic garnivorous reptiles with clongate ros 
trum, with external nares separate and placed far 
