392 GEOLOGICAL SURVEY OF THE TERRITORIES. 



tip ; the ridges straight, continuous. There are no indications of nos- 

 trils, so that these were probably posterior, and near the orbits, as in 

 Plesiosaurus. 



The pelvic arch is more extended than the scapular, and strongly 

 resembles the pelvic arch of other Plesiosauridce. The scapular arch is 

 peculiar ; the claviculi are broad, flat bones, resembling the pubes of cer- 

 tain tortoises, while the coracoids are much like the coracoids of Ple- 

 siosaurus. 



The scapular arch is remarkable for the resemblance of coracoids to 

 those of Plesiosaurus. The clavicles have a greater transverse extent 

 than the former, and have a very extensive line of union medially, and 

 a narrow posterior prolongation, which meets a similar anterior one of 

 the coracoids, separating the intervening foramina. They appear to 

 form about one-third of the walls of the glenoid cavity, and have a con- 

 stricted base, as in some Plesiosauria, applied to the extremity of the 

 coracoid. The form of the glenoid cavity cannot be readily ascertained 

 from the absence of the scapula. What we have of it would suggest 

 the existence of a fore limb, of comparatively little power, though uo 

 remains of such have been*found. The acetabulum is smaller than the 

 glenoid cavity; this point, with the obvious source of propulsive power 

 in the tail, renders it probable that the posterior limbs were the weaker 

 of the two, if any existed. But there is no trace of sacrum, nor of any 

 mod ill ed diapopyses for support of an ilium. 



The ischia are flat, sub-triangular bones, with a long median line of 

 junction, and communicating anteriorly with the posterior prolongation 

 of the pubic plate. Their postero- exterior margins project well back- 

 ward. The pubes are broad plates, whose anterior margins diverge 

 from each other. They are broader than the ischia, and form a broad 

 shallow basin for the support of the viscera. The suture defining these 

 elements is obliterated; they are continuous, and form a weak, inferior 

 keel on the median line. A simple curved ilium has been preserved, for 

 which there appears to be a smooth, articular surface on the pubis to 

 which it was attached. 



The acetabular portions of these elements are flattened and furnished 

 with convex articular surfaces. The supposed ilia are short, curved 

 bones, resembling that of Plesiosaurus latispinus, Ow., or of some of the 

 other species of that family. The shank is flattened cylindric; the 

 distal extremity, dilated, rounded, and flattened. The proximal ex- 

 tremity sub-truncate, or truncate in two or three unequal planes, and 

 with a median pit. It fits well when applied to a concavity on the 

 articular surface of the pubis. The vertebrae above the pelvic arch were 

 furnished with elongate, sub-eylindric diapophyses. 



The question as to the presence of posterior limbs remains unsolved. 

 Dr. Turner, having made a second careful search and renewed excava- 

 tions at the original locality, failed to find any bones which can be 

 assigned to humerus, ulna, radius, carpus or phalanges, or similar ele- 

 ments of the hind limbs. This is the more remarkable, as the pelvic 

 and scapular arches were further completed, and an additional number 

 of ribs obtained. The inferior and lateral regions of the trunk, being 

 then so abundantly discovered, what are Ave to think of the entire 

 absence of the usually numerous elements of extremities % The glenoid 

 cavities are rather angular, and both were filled with solid, argillaceous 

 matrix. The acetabula are not cup-like, but merely exposures of the 

 narrow, plane extremities of the pubes and ischia ; they were covered 

 with thin layers of gypsimi ; the pieces of the ilia were found imbedded 

 in the mass of matrix which occupied the pelvic arch. 



