ii 
1872.] 4355 [Cope. 
Distribution. This fossil was found near Ft. Wallace, W. Kansas. It 
was entirely recovered by excavating. The edges of one of the large 
/ bony shields were seen projecting from a bluff near Butte Creek, and was 
7 followed into the chalk rock with pick-axe and shovel with the result 
already indicated. The large bones were exposed in an entire condition, 
but were much fractured in the attempt to lift them from their bed. 
Though carefully packed, the transport of 1500 miles still further injured ili) 
\ them, and the portions described were reconstructed of over 800 pieces 
by myself. One of the bony plates was broken into 108 pieces, the ribs | 
into 183, the marginals into 146, ete. | 
This species may be called Protostega gigas, Cope.* A second species ap- I | 
pears to have existed during the Cretaceous period, as indicated by a i] 
humerus from near Columbus, Miss., sent by Dr. Spillman to the i) 
Academy of Natural Sciences. With it were received bones of the 
Mosasauroid Platecarpus tympaniticus, and Dr. Leidy, who described 
. them,{ regarded all as belonging to one animal. On this basis he ex- 
pressed the opinion that the fore limbs of the Pythonomorpha were i 
natatory. That this view was correct I proved by study of the skeleton 
of Clidastes propython, and it now appears that the fore limbs of the latter i 
were the first ever described. a 
The humerus of the Mississippi Protostega (see Leidy, 1. ¢., Pl. viii., 
Fig. 1-2) is more elongate than that of the P. gigas, and is less contracted | 
medially. The (great trochanter or) deltoid crest is longer and stouter, i 
and the process answering to the little trochanter is more prominent, 
rounded, and proximal in position. It indicates a rather smaller animal 
than the Kansas specimen, and may be named Platecarpus tuberosus. 
A third species is represented by a humerus found in the cretaceous 
green-sand of New Jersey. lt was a huge animal, exceeding not only | 
j the species just described, but even the Indian Colossochelys atlas. 
i usually regarded as the largest of the order. It was regarded by Leidy 
| as pertaining ‘‘to the great Mosasaurus,”’ but Agassiz regarded it as 
Chelonian in affinities, naming it <Atlantochelys mortonii.t Its great 
trochanter is very prominent, as in P. tuberosus, but the lesser one is 
smaller and nearer the condyle or head. The shaft is still more slender 
and not flattened, but subcylindric. It may be called Protostega neptunia. 
‘ It is figured by Leidy, 1. ¢. Pl. viii. fig. 8, 4. In this connection may be 
recalled the vertebrae of a gigantic animal from the New Jersey Cre- 
taceous, described by the writer as belonging to an extinct species and 
genus under the name of Pnewmatarthrus peloreus. Tt is quite likely 
that these belonged to a turtle still larger than the Protostega neptunia. 
(See Proceed. Amer. Philos. Soc., 1870, p. 446.) 
*Proceed. Amer. Philos. Soc. 1871, p. 173. 
+ Cretaceous Reptiles of North America, p. 42. Smithson, Contrib. 1864, 4 
+ This name was unaccompanied with the necessary description, and is hence useless to 
seience, 
A. P. S.—VOL. XII.—3C Hi 
