120 MEMOIRS OF THE CARNEGIE MUSEUM 
it has already been shown that two 
specimens in this museum, Nos. 603 and 
878, have a surface on the infero-pos- 
terior margin of the axis as if for the 
articulation of such a bone. However 
this element has never been found in 
place. 
7. “The development of large 7. The coracoids of O. icenicus ex- 
facets upon the interior margins of the amined by me at the American Museum 
coracoids.” of Natural History, New York, N. Y., 
show well-developed surfaces for artic- 
ulation with one another medially. 
Combining the characters given by Marsh and Knight with those shown by the 
material under discussion the genus Paptanodon may now be distinguished by the 
| following characters : 
Gen. char.: Teeth present but loosely attached.  Dentition somewhat reduced but ea- 
tending the entire length of the jaws. Opisthotic reaching and partially enclosed by the 
squamosal. Reduced number of hypocentra. Vertebral centra forward of the posterior 
caudals uniformly biconcave. Ribs of the anterior part of the skeleton double-headed. 
Clavicles firmly united. Well developed interclavicle present. Coracoids without pos- 
terior notch and wniting im the median line by large elliptical facets. Humerus with 
strongly developed trochanteric ridge on dorsal surface and having three wnequal facets 
on the distal extrenuty, which articulate with three irregular polygonal elements in the 
epipodial row. All remaining bones of the anterior extremities more or less rownded 
and retained in persistent cartilage. 
Three species of this genus have been described, of which a brief review is given 
in the following pages. 
Bapranopon NATANS, Marsh. 
Sauranodon natans, Marsh, O. C., Amer. Jour. of Sci., Vol. X VII., 1879. 
Baptanodon natans, Marsh, O. C., Amer. Jour. of Sci., Vol. XIX., 1880. 
Ophthalmosauwrus natans, Lydekker, R., Geol. Mag., Vol. V., 1888. 
Baptanodon natans, Lydekker, R., Cat. of Fossil Reptilia and Amphibia in the British 
Museum, Part II., 1889. 
This species, the type of the genus, was based upon a considerable portion of a 
skull, a number of vertebree and ribs, and parts of one or more limb bones. As has 
been shown previously hardly any of the original characters given for this species 
can be considered valid. 
