GEOLOGICAL SUEVEY OF THE TERKITORIES. 387 



to the dorsal ; only two indicate the characters of the cervical verte- 

 brae. All of these vertebrae, except the distal caudals, are remarkable 

 for their short anteroposterior diameter and deeply-concave, articular 

 faces. This concavity is not, however, of an open conic form, as in 

 Ichthyosaurus, but is flattened at the fundus, thus exhibiting a small, 

 slightly disciform area. The usual pair of venous foramina appears on 

 the under side of the centrum. The neural arch is continuous with the 

 latter, and exhibits no trace of connecting suture. The diapophyses 

 arise from the neural arch in all the dorsals ; they are compressed and 

 vertical in section. The arch is of course narrow anteroposteriorly, and 

 presents a pair of moderately prominent zygapophyses in each direction, 

 the posterior as usual articulating downwards, the anterior upwards. 

 On some of the vertebrae they become closely approximated. The neu- 

 ral spines are narrow anteroposteriorly, but much stouter transversely 

 than in EJasmosaurus ; they are strongly grooved at the base, both an- 

 teriorly and posteriorly, most so posteriorly. 



The caudal vertebrae are anteriorly quite as large asthe dorsals. Two 

 anterior caudals present, on the latero-inferior part of the posterior mar- 

 gin, a pair of widely-separated, articular surfaces for chevron bones. 

 A portion of one of the latter remains ; it is narrow and subcylindric at 

 the base. The diapophyses are situated on the upper part of the cen- 

 trum, and are continuous with it, and without trace of suture. There 

 are two distal cervicals which are much smaller than the preceding. 

 They are solidly coossifled and have been broken from one anterior to 

 them, with which they have been also ankylosed. Processes in the po- 

 sition of the diapophyses have disappeared, while a strong infero-lateral 

 process projects from the middle of each, similar in position to the para- 

 pophyses (or whatever they may be) of the JUlasmoscwrus. These pro- 

 cesses are decurved and much thickened and rugose; they may be de- 

 scribed as more or less elongate conic. The neural canal of these ver- 

 tebrae is well marked, though small. The coossiiication of cervical ver- 

 tebrae is a remarkable character, and very unusual. It does not seem 

 probable that these specimens represent a diseased condition, since they 

 are symmetrical, and the inferior surface and foramina are unaffected. 

 The rugosity is much that of a ligamentous articulation. Their size in- 

 dicates a remarkably slender neck as in Plesiosaurus, but even more so, 

 and perhaps as elongate as in Masmosaurus. 



That the portions of an extremity alluded to belong to the posterior is 

 rendered probable by the presence of part of an ilium, and by the fact 

 that the portions of the vertebral column secured are chiefly median and 

 posterior. The fragments consist of the extremity ot the femur, the tibia, 

 several tarsal bones, and numerous phalanges. The whole limb is of 

 great size, compared with the vertebral column, and indicates power- 

 ful natatory capacity in its possessor. What the relative length of 

 the femur may be cannot be ascertained, as the proximal portion is want- 

 ing, but if it were like the tibia it was characterized by stoutness rather 

 than by length. The portion remaining is flattened, and presents distally 

 two distinct articular faces for ulna and radius, instead of the uniformly 

 convex outline characteristic of most of the species of Plesiosaurus. The 

 tibia is pentagonal, broader than long, and not emarginate externally. 

 The fibula is wanting. One of the tarsal bones is a flat, unequally hex- 

 agonal disk, of less thickness than the tibia and the tarsals which appear 

 to connect with it. One of the latter is transverse parallelogrammic, 

 with three faces of broad plane articulations and the outer edge rounded 

 in section. Another tarsal or metatarsal is a parallelopipedou except 

 that one extremity presents two faces meeting at a right angle. Another 



