SEA-SERPENTS 



discovered by Dr. Williston, complete in nearly every detail. The 

 restoration of the skeleton of Platycarpus, shown in Plate XXX., 

 is based chiefly on one specimen, but certain parts are supplied 

 conjecturally from Tylosaurus. The latter has been restored, as 

 to its skeleton, from three specimens found by Dr. Williston, 

 who was fortunate enough to find an impression of the skin, 

 near one of the paddles, showing small scales, rather like those 

 of a snake, but these were too small to be shown in our 

 restoration (Plate XXXI.) of Tylosaurus. Platycarpus seems to 

 be intermediate between Clidastes and Tylosaurus. In Clidastes 

 we see a very long body, and a shorter tail, but this tail must have 



FIG. 70. Superior aspect of the cranium of Platycarpus curtirostris, Cope ; from 

 the Upper Cretaceous of N. America (greatly reduced). (After Cope.) 



been a powerful organ of propulsion. The limbs were strong 

 and flexible, and the movements of this Mosasauroid reptile were 

 more snake-like. The vertebrae in the tail had their neural 

 arches lengthened, and probably the tail had a fin-like expansion 

 to help in propulsion, as in the case of eels. 



The accounts given by Professor Cope of his explorations and 

 the difficulties encountered in procuring the valuable specimens 

 on which his conclusions are based, are most interesting, and 

 such as every fossil hunter will appreciate. We, in England, 

 who visit clay pits, stone quarries, railway cuttings, etc., during 

 a morning or afternoon walk, and return home at our leisure 



