No. 525] THE SAUROPODOUS DINOSAURS 551 



as Alios aur us, Tyrannosaurus, Trachodon or Campto- 

 saurus, admittedly erect-walking bipedal forms, with the 

 femora of the Sauropoda. we iind a great difference iu the 

 quality of the bone and the finish of the articulations. 



The shaft of the former appears to be more elaborately modelled, and 

 to consist of finer and harder bone; all the articular surfaces are smooth 



layer of cartilage, are preserved: there is a definite head, separated 

 from the shaft by a distinct neck, and nearly filling the acetabulum; 

 and there is a definitely formed trochanter major. In the Sauropoda, 

 on the contrary, the shaft seem- to be composed of coarser bone; the 

 articular surfaces are rough and show that they were covered by a 



It is not clear what lizards Dr. Hay had here in mind. 

 The larger land lizards have a much more " differenti- 

 ated " femur. Even in the crocodiles the resemblance is 

 not'very close. But a much closer and more striking re- 

 semblance in the characters cited may be found if we 

 compare the femora of large aquatic reptiles, ichthyo- 

 saurs, mosasaurs or plesiosaurs, or large aquatic mam- 

 mals such as the Cetacea, with the femora of the Sauro- 

 poda. The reviewer would agree entirely with Dr. Hay 

 that the lack of differentiation and finish in the limb bones 

 of Sauropoda is a strong argument that they were not 

 adapted to the habitual support of the whole weight of 

 the body. But the evidence cited accords exactly with the 

 theory of Owen and Cope that they were wading animals, 

 and the limbs were designed for the support of the body 

 in the water, with most of its weight buoyed up thereby. 



Dr. Hay believes that the position of the great trochan- 

 ter in the Sauropoda was well down on the shaft, as it is 

 in the Triassic Theropoda; but he fails to give any good 

 reason for rejecting Osborn's view that the very clearly 

 marked rugosity around the proximal-external angle of 

 the head is the area of attachment of the gluteal muscles. 



