GILMORE: OSTEOLOGY OF BAPTANODON (MARSH) 125 
of being a normal character, may be due to pathological conditions as has been 
shown to exist in the extremities of the Mososaurs.” 
The species was based upon a considerable portion of the pectoral girdle, with a 
part of the right fore limb and 41 consecutive vertebre extending from the atlas 
posteriorly. 
A comparison of the coalesced atlas and axis of B. marshi, with the same ele- 
ments of B. discus appears to show differences that would serve for specific separa- 
tion, 2. e., the reduced number of intercentra, shown by the absence of the apophy- 
sis on the axis for the third incentrum, and the reduced size of the parapophyses of 
the third and fourth cervicles. These were certainly not functional in this species. 
Some other minor differences will be noted by comparing Figs. 10 and 26. 
With these exceptions and the arrangement of the bones of the paddle the other 
parts preserved do not differ materially from the corresponding elements of B. discus. 
The type is specimen “S”’ preserved in the Jurassic collections of vertebrates of 
the University of Wyoming, at Laramie, Wyoming. This specimen was collected 
by Mr. W. H. Reed from the Baptanodon Beds of the Jurassic in the Northern part. 
of Albany Co., Wyoming, in 1897. 
DiscussIoN OF THE GENUS OPHTHALMOSAURUS. 
In studying the genus Baptanodon it was necessary to review the literature per- 
taining to the closely allied genus Ophthalmosaurus. Having this at hand and 
because of the great similarity of the two forms it is believed that a brief review of 
that genus would be appropriate at this time. 
The type species is O. icenicus founded by Seeley” on the greater portion of the 
pectoral girdle. |The important characters by which he distinguishes this genus 
from Ichthyosawrus are the peculiar conditions found in the clavicular girdle, 7. ¢., 
the separated clavicles, the enclosing of the anterior part of the interclavicle in a 
groove of the clavicles, and the embracing of the anterior margins of the coracoids 
by the clavicles. 
Further characters were made known by the description of a portion of the fore 
limb of a second individual which is larger and better preserved than the corres- 
ponding elements of the type. These differences are as follows: distal end of hu- 
merus articulating with three bones, radius, ulna and olecranon (pisiform of modern 
nomenclature) and the carpus with a row of four elements. 
The characters cited above constitute all of the essential differences given. The 
somewhat remarkable supposition that the clavicles encircled the coracoids is due 
55 Williston, S. W., ‘‘ Univ. Geol. Survey of Kansas,’’ Vol. IV., PartI., p. 244. 
56Seeley, H. G., Quart. Jour. Geol. Society of London, Vol. XXX. 
