42 MOSASAURUS. 
webbed, but the remains which have been discovered, on the contrary, do not lead 
to the supposition that it possessed fins like the Jchthyosaurians.' 
Prof. Owen,’ after remarking that no part of the organization of Mosasaurus is 
so little known as that of the locomotive extremities, and substantially quoting the 
views of Cuvier, expressed above, enters into the description of some long bones of 
the extremities, “‘ showing the Lacertian type of structure,” which were obtained in 
the Green-sand formation of New Jersey. Professor Owen observes, “on the highly 
probable supposition that these bones belong to Mosasaurus, they indicate the ex- 
tremities of that gigantic Lizard to have been organized according to the type of 
the existing Lacertilia and not of the Enaliosauria or Cetacea.” 
Pictet? says the humerus of Mosasaurus is thick and short, like that of Ichthyo- 
saurus, but gives no evidence for this assertion. He adds, we may conjecture, from 
the flattening of the bones of the members, that the feet were probably converted 
into fins like those of the Enaliosaurians. 
Some remains, apparently of MJosasaurus, which I have the opportunity of ex- 
amining, indicate the limbs to have been fins, partaking in their structure the 
characters of those of the marine Turtle and the Plesiosawrus. 
The humerus previously mentioned, found in association with several cervical 
vertebrie, a tympanic bone, and a pterygoid with teeth, submitted to my inspection 
by Dr. Spillman, of Mississippi, is represented in Figs. 1, 2, Plate VIII. Having 
every appearance of belonging to the same skeleton as its associated bones, there 
can be but little doubt of its appertaining to Mosasaurus or one of its allies. 
The specimen is of the right side, and bears a striking resemblance to the humerus 
of a Turtle, with which I suppose it to have corresponded in the relative position of 
its parts, and shall, therefore, so describe it. 
The shaft is short and rapidly expanded towards the extremities. Its middle 
part is cylindrical, but much compressed antero-posteriorly. The borders form a 
deep curve in the length, and are transversely convex, but the outer is the more 
obtuse. The posterior surface, Fig. 1, is transversely convex; the anterior, Fig. 2, 
nearly flat, and marked just above the middle by a roughness (d) for muscular 
attachment. 
The proximal extremity expands to more than three times the breadth of the 
middle of the shaft. A demi-spheroidal head (a) projects forward, midway between 
two tuberosities, and is partially sustained in the usual manner by a gradual uprising 
abutment of the shaft. The tuberosities include a deep concavity back of the 
head, and are associated by the posterior terminal portion of the shaft, which presents 
a broad and slightly concave surface extending between them. The greater tuber- 
osity (4), situated postero-superiorly, extends a short distance proximally beyond the 
head so as to increase the length of the bone. It is compressed antero-posteriorly, 
and, in the specimen, is imperfect at the summit. The lesser tuberosity (c), situated 
1 Op. cit., p. 196. Da sie sich im Meerwasser aufhielten, so waren die Zehen ihrer Fiisse ohne 
Zweifel mit Schwimmhiuten verbunden; die gefundenen Knochenreste lassen dagegen nicht vermuthen, 
_ dass die Flossenfiisse, wie die Fischeidechsen gehabt hatten. 
2 British Fossil Reptiles, p. 190 8 Traité de Paléontologie, Ed. 2, T. 1, p. 505. 
