ORDER DINOSAURIA. 1175 



American types are generically distinct from those to be now 

 mentioned. 



We may now proceed to the consideration of certain European 

 Dinosaurs which from their more or less close alliance to the pre- 

 ceding forms appear to belong to the same family, although opinions 

 to the contrary have been expressed. It may be observed in this 

 connection that the study of all the European Sauropoda is beset 

 with almost insurmountable difficulties owing to the circumstance 

 that nearly all the specimens are disassociated, and that genera and 

 species have been named on the evidence of single teeth, vertebrae, 

 or bones of the limbs or limb-girdles, so as not to admit of com- 

 parison with one another. Moreover, the unwieldy bulk of the 

 specimens themselves is a bar to an exact comparison, even when 

 they are strictly comparable one with another. 



The tooth from the Wealden of the Isle of Wight, represented 

 of the natural size in fig. 1075, has been made the type of the 

 genus Hoplosaurus (Oplosaurus), and it appears almost certain that 

 cervical and dorsal vertebrae, and a pelvis from the same deposits, 

 described under the names of Ornithopsis Hulkei and O. eucamerotus, 

 are referable to the same form. These remains indicate a Reptile 

 of considerably smaller dimensions than Brontosaurus, having a 

 pelvis which approximates in structure to that of Atlantosaurus. 

 The ischium, which has the downward direction characteristic of 

 the present family, has a length of 27 inches, and is comparatively 

 wide in proportion to the pubis. The genus Pelorosaurus is typified 

 by a huge humerus from the Wealden of Sussex, measuring some 

 54 inches in length, which would appear far too large for the type 

 species of Hoplosaurus} A slightly larger humerus from the Kim- 

 eridge Clay, originally described as Cetiosaurus humerocri status, 

 appears generically inseparable from Pelorosaurus, and its owner 

 was in all probability very closely allied to an equally large form 

 from the Oxford Clay, described upon the evidence of the pelvis as 

 Ornithopsis Leedsi. Of the latter the lumbar and caudal vertebrae 

 are also known, and approximate closely, both in size and contour, 

 to those of Brontosaurus, the lumbars having a diameter of nearly 

 1 2 inches across the centrum. In the pelvis the ischium measures 

 nearly 36 inches in length, and is also narrower in proportion to the 

 pubis than in Hoplosaurus — differences which, coupled with others, 

 may probably be regarded as of generic value. Referring all these 

 forms, at least provisionally, to Pelorosaurus, it would appear that this 

 genus includes very large Dinosaurs closely allied both in vertebral 

 and pelvic characters, as well as in point of size, to Brontosaurus, al- 



1 Compare the proportions of this bone and of the ischium mentioned below 

 with the corresponding dimensions of other Dinosaurs given in the table on the 

 next page. 



VOL. II. T 



