86 Bevieivs — Dollo's Dinosauria of Bernissart. 



individuality in the sternum of Dinosaurs, as in the plastron in 

 Chelonians. The sternal ossification, anterior to these xiphoid 

 elements, which is seen in the fossil figured by Mr. Hulke, is thin, 

 and is not commonly preserved. The anterior extremity of this 

 Dinosaurian structure is at present unknown. The posterior xiphoid 

 ossification may have been connected with the prepubic bones, 

 in much the same way as the abdominal ribs of Crocodiles extend 

 down to the pubic bones. 



In the third paper M. Dollo discusses the attitude of the Iguano- 

 don. First, there is the view originated by E. D. Cope that they 

 progressed chiefly upon their posterior limbs, in the manner of the 

 Eatita3, of which they were supposed to be the parent stock. 

 Secondly, I have accepted the bipedal progression, but denied that 

 these Dinosaurs are the ancestors of Birds. And, thirdly. Sir K. 

 Owen regards them as having been exclusively aquatic, with the 

 body carried in a horizontal position. In support of the upright 

 position, it is urged that there is a remarkable correspondence 

 between the pelvis of Iguanodon and that of Ratite Birds ; while the 

 difference in structure between the fore and hind limbs of Iguanodon ; 

 the relative dimensions of the head and thorax as compared with 

 quadruped reptiles ; the nature of the vertebral column ; and the 

 Wealden footprints described by Beckles and other writers furnish 

 conclusive evidence. Each of these points is considered in detail. 



The author begins by discussing the pelvis, and endeavours to- 

 combat the views of Sir E. Owen, and to prove that the ilium 

 of Iguanodon agrees in the most striking manner with the homo- 

 logous element in Birds. I am not concerned to do more than urge 

 that the author rather undervalues the resemblances to the ilium, 

 of a Crocodile. If we begin with the geological history of the 

 Dinosaurian ilium, and trace it in development through successive 

 generic types of evolution, I do not see how the conclusion can be 

 resisted that the Dinosaurian ilium is a modification of the Croco- 

 dilian ilium, which only resembles the ilium of a bird in such ways 

 as indicate a modification of the Crocodilian plan. This plan of the 

 Dinosaurian ilium, as seen in such types as Zanclodon and TTieco- 

 dontosaurns, is remarkable for the mass of the bone lying behind the 

 acetabulum, as in Crocodiles. The form of the post-acetabular part 

 is wonderfully alike in both groups. And the difference begins 

 with the Dinosaurian elongation of the pedicle for the pubis, which 

 throws the bone upward, and the concurrent elongation of the 

 preacetabular process, which at first is so short as not to extend in 

 advance of the acetabulum. Even when the latter process is 

 elongated, as in Iguanodon Mantelli, or J. Bernissartensis, it 

 never loses trace of its origin, or approximates to the ilium of a bird 

 in form, any more than in osteological connections ; though the 

 ilium of Stegosaurus makes perhaps as near an approximation to 

 the Ratite contour as is seen in a Dinosaur. The ischium and pubis 

 of Iguanodon are treated by M. Dollo in the same spirit, with the 

 conclusion that the ischium in Dinosaurs, and especially in Iguano- 

 don, shows a strong avian resemblance, while in the pubis there is ■ 



