Principal Forms of the Dinosauria. 325 



The vertebrse, also, and especially the pelvic arch, afford 

 distinctive characters. By the latter alone, the Atlantosauridw 

 and Morosawidce may be readily distinguished. In the 

 absence of the skull, this is a point of importance in a compari- 

 son of European with American forms. 



In the Atlantosauridw, the ischia are nearly straight, and 

 when in position, extend downward and inward, meeting on 

 the median line by a symphysis of the two ends, as in croco- 

 diles. In the Morosauridce, the ischia are twisted, and extend 

 inward and backward, with the inner margins alone meeting 

 each other on the median line, the ends being free. 



All the ischia of Sauropoda known from Europe appear to 

 be of the latter type, although proportionally broader and more 

 massive than those of the corresponding American forms. 

 The ilia and pubes associated with these ischia agree in their 

 main features with those of the American genus Morosaurus, 

 so that there can be little doubt that the same general form is 

 represented in both countries. 



A striking difference between the Cetiosauridce and the 

 allied American forms is that, in the former, the fore and hind 

 limbs appear to be more nearly of the same length, indicating 

 a more primitive or generalized type. Nearly all the Ameri- 

 can Sauropoda, indeed, show a higher degree of specialization 

 than those of Europe, both in this feature and in some other 

 respects. 



The identity of any of the generic forms of European Sau- 

 ropoda with those of America is at present doubtful. In one 

 or two instances, it is impossible, from the remains now known, 

 to separate closely allied forms from the two countries. Por- 

 tions of one animal from the Wealden, ref erred by Mantell to 

 Pelorosaurus under the name P. Becklesii* are certainly 

 very similar to some of the smaller forms of Morosaurus, 

 especially in the proportions of the fore limbs which are 

 unusually short. This fact would distinguish them at once 

 from Pelorosaurus, and until the skull and more of the skele- 

 ton are known, they cannot be separated from Morosaurus, 

 and should be known as Morosaurus BeeMesii. During the 

 examination of this specimen, which is in the collection of its 

 discoverer, Mr. S. H. Beckles, of St. Leonards, England, the 

 author found, attached to the humerus, portions of the osseous 

 dermal covering, the first detected in the Sauropoda, and 

 known only in the present specimen. 



A dozen or more generic names have been proposed for the 

 European forms of Sauropoda, and of these, Cetiosaurus, 



* Morris' Catalogue of British Fossils, p. 351, 1854. 



