42 MOS AS AURUS. 



webbed, but the remains which have been discovered, on the contrary, do not lead 

 to the supposition that it possessed fins like the Ichthyosaurians} 



Prof. Owen,^ after remarking that no part of the organization of Mosasaiirtis 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 tj-pe of 

 the existing Lacertilia and not of the Enaliosauria or Cetacean 



Pictet^ says the humerus of Mosasaurus is thick and short, like that of IcJitliyo- 

 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 EnaJiosaurians. 



Some remains, apparently of Mosasaurus, 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 Plesiosaurus. 



The hiimerus previously mentioned, found in association with several cervical 

 vertebrte, 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 antcro-posteriorly. The borders form a 

 deep curve in the length, and are transversely convex, but the outer is the more 

 obtuse. The posterior siurface, Fig. 1, is transversely convex; the anterior, Fig. 2, 

 nearly flat, and marked jvist above the middle by a rouglmess (d) for muscular 

 attachment. 



The proximal extremity expands to more than three times the breadth of the 

 middle of the shaft. A demi-sphcroidal 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 (5), 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 



' Op. cit., p. 196. Da sie sich iin Meerwasser aufhielten, so waren die Zehen ihrer Fiisse oline 

 Zwcifel mit Schwimmhi'iuten verbundeu ; die gefundenen Kiiochenreste lassen dagegen niclit vermuthen 

 dass die Flo.ssenfusse, wie die Fischeideclisen gehabt hatten. 



' British Fossil Reptiles, p. 190 « Traite de Paleoiitologie, Ed. 2, T. 1, p. .')05. 



