71 



been Ijiokeii i'nnn one anterior to them, with which they have been also anchy- 

 losed. Processes in the position of the diapophyses have disappeared, while 

 a strong infero-lateral process projects from the middle of each, similar in 

 position to the parapophyses (or whatever they may be) of the Elasmosnurus. 

 These processes are decurved, and much thickened and rugose; they may be 

 described as more or less elongate-conic. The neural canal of these vertebrae 

 is well-marked, though small. The coossitication of cervical vertebra? is a 

 remarkable character, and very unusual. It does not seem probable that these 

 specimens re])resent a diseased condition, since they are symmetrical, and the 

 inferior surfaces and foramina are unaffected. The rugosity is much that of 

 a ligamentous articulation. Their size indicates a remarkably slender neck, 

 even more so than in Pleswsaurus. 



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 of the femur, the tibia, several tarsal 

 bones, and numerous phalanges. The whole limb is of great size compared 

 with the vertebral column, and indicates powerful natatory capacity in its 

 possessor. What the relative length of the femur may be cannot be ascer- 

 tained, as the proximal portion is wanting ; 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 emarginate 

 externally. The fibula is not preserved. One of the tarsal bones is a flat, 

 unequally hexagonal disk, of less thickness than the tibia and the tarsals, 

 which appear with three faces of broad, plane articulations, and the outer edge 

 rounded in section. Another tarsal or metatarsal is a parallelopipedon, except 

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

 similar, but oblirpie, i. e., rhombic in section; one of the longitudinal angles 

 is also prolonged. 



Of the phalanges, there are individuals from three series. Portions of 

 ilat ixMies, perhaps belonging to the pelvic arch, indicate, as do all tlie other 

 pieces, that tlie bony structure in Polycotylus is more nuissive than in Elas- 

 mosaurus, if the only known species has not attained such huge dimensions as 



