GILMORE: OSTEOLOGY OF BAPTANODON (MARSH) 121 
B. natans is typically the smallest species of this group. In fact until the type 
specimen is properly prepared and redescribed this is the only way by which B. 
discus may be distinguished from this form. The teeth when better known may 
show specific differences. The one tooth discovered of B. natans has «a smooth 
enameled surface as contrasted with striated surfaces of the teeth of B. discus. 
The type No. 1952 was collected by Mr. W. H. Reed, in the vicinity of Como 
Bluff, Albany Co., Wyoming, and is now preserved in the collections of the Yale 
Museum, New Haven, Conn. 
Bapranopon piscus, Marsh. 
Sauranodon discus, Marsh, O. C., Am. Jour. of Sci., Vol. XIX., 1880. 
Baptanodon discus, Marsh, O. C., Am. Jour. of Sci., Vol. XIX., 1880. 
Ophthalmosaurus discus, Lydekker, R., Geol. Mag., Vol. V., 1888. 
Baptanodon discus, Lydekker, R., Cat. of Fossil Reptilia and Amphibia in the British 
Museum, Part II., 1889. 
Microdontosaurus petersonii, Gilmore, C. W., Science, N. S., Vol. XVI., 1902. 
This species was based upon a portion of a poorly preserved skull, numerous 
vertebree including the coalesced atlas and axis, left coracoid, with the greater portion 
of the left pelvic (?) paddle and numerous fragments of other portions of the skeleton. 
It is with considerable trepidation that I assign the specimens considered in this 
paper to the species discus, but after a somewhat superficial examination of the type 
I was unable to find differences of sufficient importance to warrant the establishment 
of a new species as was proposed in a previous paper. The study of the type was 
superficial to the extent of trying to determine characters from material that has 
been but little prepared. The parts of the skull exposed only show a small area 
of the mid-portion of the rostrum and one sclerotic ring; the other parts are either 
wanting or covered by the very refractory matrix. The characters shown by the 
parts of the skull exposed together with the atlas and axis and left coracoid are the 
principal elements upon which my comparisons were based. The great similarity 
of these elements to the corresponding parts of oar specimens prompted me to the 
present determination. 
The type specimen No. 1955 is preserved in the vertebrate collections: of the 
Yale Museum, New Haven, Conn. It was collected by Mr. W. H. Reed in 
Wyoming. 
3APTANODON MARSHI, Knight. 
Baptanodon marshi, Knight, W. C., Amer. Jour. of Sei. (4), Vol. XV., 1903. 
In the characterization of this species Dr. Knight distinguished it from all 
others by the shape and arrangement of the bones of the fore paddle. The two 
