678 SCIENCE PROGRESS 



Greenland and Iceland to Europe, and so on to India, Africa, 

 Madagascar, and Australia. The Sauropoda, on the contrary, 

 appear to be an Old World group which migrated early in the 

 Jurassic into " Gondwanaland," and likewise into the New 

 World. In the southern hemisphere this group had a distribu- 

 tion nearly as extensive as that of the carnivorous theropods, 

 and survived long after the latter had disappeared from the north, 

 occurring in India during some part of the Cretaceous, and in 

 Patagonia during the Laramie or topmost Cretaceous. On 

 account of their semi-aquatic habits these dinosaurs were in- 

 dependent of complete land-connection, and able to extend their 

 migrations across areas impassable to the terrestrial iguanodon 

 and its relatives. This may be the reason why the latter group, 

 so far as is known, never succeeded in reaching the southern 

 hemisphere, although it is possible that the date of their radiation 

 may have been later, when communication between Europe and 

 Gondwanaland was interrupted. It has also to be borne in mind 

 that, judging from their dentition, iguanodonts were dependent 

 upon a particular kind of food. Originally the Ornithopoda 

 were probably North American, and among them the Ceratopsia 

 appear to have been always restricted to the western continent. 



The pose of the limbs in sauropod dinosaurs was much 

 discussed in 1909, and the subject has been resumed in the 

 year under review. 



In the American Naturalist, vol. xliv. pp. 259-83, for instance, 

 Dr. W. J. Holland discussed the views of Dr. Tornier and 

 others on the pose of the limbs of Diplodocus. In his criticism 

 the author emphasised the marked distinctness of the Dino- 

 sauria from other reptiles, and suggested that this might in 

 some degree be sufficient to render it probable that their limbs 

 approximated to the mammalian type in regard to the relative 

 position of their bones. Evidence of this is afforded by the 

 compressed, instead of depressed, form of the thoracic cavity, 

 which appears incompatible with limbs arranged in crocodilian 

 fashion. It is shown that if the femur is placed, as suggested 

 by Dr. Tornier, in a horizontal plane, its head cannot be made 

 to enter the acetabular cavity of the ilium, while, on account of 

 projections, no movement would be possible. In this mode 

 of restoration the distal articular surfaces of both humerus and 

 femur project at right angles to the axes of the bones of the 

 lower segment of the limbs without being opposed to the 



