434 Bevieivs — Leidy's Cretaceous Reptiles. 



those of Plesiosaurus, and the animal appears to have been only a big- 

 headed Piesiosaur with short neck- vertebrae. In these and most 

 other characters (except the trigonal teeth) Polyptychodon resembles 

 Pliosaurus. 



Hi/posaiirus Bogersi (Owen) has both articular surfaces of the ver- 

 tebral centrum flattened and slightly concave, with an hypapophysis, 

 sometimes more developed than in the Alligator. In other respects it 

 is aj^parently a true Crocodile. We do not conceive the flattening 

 of the vertebrse to be important as a mark of affinity, or as a 

 classificational character ; but for what it may be worth it is a 

 point of resemblance between Kyposaurus, Steneosaurus, and Teleo- 

 saurus. 



The Chelonians are eight species. Trionyx priscus is founded on 

 part of a costal plate. It is of Tertiary type, coarsely marked, 

 and unlike the Trionydian remains from the Cretaceous strata of 

 Europe. Bothremys Cooki, this is a very extraordinary Emydian 

 Chelonian ; the author compares it to Podocnemys, but we are unable 

 to discover more than the faintest affinity with that genus. There 

 are slight indications of affinity with Trionyx. There are curious 

 pits in the palatal part of the maxillary which the author suggests 

 may have been for corneous teeth. 



There is no evidence that either Chelone sopita or C. ornata 

 belong to the genus to which they are referred, or that they belong 

 to different species. That specimen referred to C. sopita has a 

 decidedly Emydian aspect. A small Platemys, indicated by fragments 

 of the plastron, is of the type represented by the London Clay P. 

 Bowerhankit. It is the Emys pravus of Prof. Leidy. The other 

 Chelonian fragments are too imperfect to make much of, they are 

 named Emys firmus, E. heatus, and Platemys sulcatus. 



The article on Mosasaurus adds little to our knowledge. The 

 teeth are treated of in great detail, but the only fact of interest 

 demonstrated, previously figured by Goldfuss, is the union between 

 the crown and the osseous pulp, which is quadrate. The chief 

 novelty is a tlieory of the limbs, in which a humerus of Chelonian 

 character, and smaller bones of the extremities of Plesiosauroid 

 character are referred to Mosasaurus. These bones we regard as 

 belonging severally to Emydian Chelonians and to Plesiosaurus. 

 Accepting, as Prof. Leidy does, Cuvier's Lacertian interpretation of 

 Mosasaurus, a more incongruous thing could not have been done 

 than to refer to it such bones as these, which might have been 

 united to a Crocodile without comment, but not to a Lizard without 

 any evidence of Chelonian affinities. The chief interest of the 

 monograph centres in Hadrosaurus, a Dinosaur with teeth of Igimnodon 

 type, denticulated at the margin and with one mesial ridge. The 

 vertebrae and limb -bones and ilium, etc., are figured. The material 

 here is all that could be wished; but as in the previous cases our 

 author has been content with topographical description, and has 

 disdained the laurels of the comparative anatomist, except in so far 

 as they are gained by vague suggestions of affinity with Iguana and 

 Iguanodon. Hadrosaurus was kangaroo-like in the proportions of its 



