558 



THE AMEBIC AS NATURALIST [Vol. XLIV 



first i> unknown; and sixteen eervicals, of which the first 

 i pro-atlas) is unknown. The problematic bone identified 



as epistenmm, is the first rib. 



Some of the points cited may he questioned or dis- 

 proved, 1 but the main contention, that the Sauropoda 

 were walking, not crawling animals appears to be abun- 



Nevertheless, there is a great deal yet to be said on the 

 pose and habitat of the Sauropoda. and there are certain 

 lines of evidence which none of the authors cited have 

 considered adequately. 



In the first place, the nature and cause of the paral- 

 lelism between sauropod dinosaurs and elephants has not 

 been very clearly pointed out. The type of limb and foot 

 structure which they show in common was first clearly 

 defined, so far as the reviewer is aware, by the late Pro- 

 fessor Gaudry, under the name of ' ' rectigradism. ' ' It 

 is a specialization directly associated with gigantic size, 

 the limb becoming straight and pillar-like, the foot short, 

 round, heavily padded, with toes reduced or vestigial. 

 The movements of the limb are chiefly at the upper joints, 

 the foot serving chiefly as pad or cushion to absorb the 

 shock in locomotion. This is very different from the 

 typical " digitigradism " of the dog or cat; it may be 

 observed with modifications, in large plantigrade and 

 unguligrade animals as well as in digitigrade forms, and 

 a progressive approach towards it may be observed in all 

 races of land vertebrates as they approach gigantic size. 

 The proximal segments of the limbs tend to become longer 

 and straighter, their articulations more terminal, the 

 distal segments shorter, their range of movement de- 

 creasing, the toes become much shortened and vestigial, 

 buried in an elastic pad, or, as in ungulates, with a broad 

 horny hoof, which absorbs shock less completely but gives 



