358 Rev. H. N. Hutchinson — Observations on 



form a mental picture of Diplodocus as it lived, we must constantly 

 bear in mind that it belongs to a rather generalized sub-order of the 

 Dinosauria, and that among recent reptiles the Crocodile is the 

 nearest thing to it. 



With regard to the extremities of the limbs, the hind foot and 

 manushave been given positions which may be described as plantigrade 

 on the whole, but not so much so as the crocodile or the lizard. 



The photograph of the model seen in Plate XXIII will serve to 

 show that the writer has endeavoured to steer a middle course between 

 the extreme view of Dr. J. B. Hatcher on the one hand and 

 Dr. Tornier on the other (see Fig. 2). 



Habits. 



With regard to the habits of this creature, there have been great 

 differences of opinion. The late Dr. J. B. Hatcher, whose valuable 

 papers on this subject the writer has read with great interest, was at 

 first inclined to believe that Diplodocus was an aquatic reptile, but 

 subsequently he somewhat modified his views, and in his latest 

 paper (Memoirs of the Carnegie Museum, vol. ii) he gives reasons for 

 thinking that the habits of the creature were mainly terrestrial. 

 The present writer is not inclined to adopt this view, but considers 

 that Diplodocus spent much time in the waters of the rivers and lakes 

 in those far-off Jurassic times. 



To take one reason only, it is difficult to imagine this great 

 creature supporting such a long neck and a still longer tail on dry 

 ground. When, standing up the strain of supporting so much weight 

 might become too excessive, but by taking to the water and resting 

 there such strain would be greatly relieved. Perhaps the shape of the 

 jaws and of the proximal end of the skull, which is decidedly duck- 

 like, helps to confirm this view. The swan has a long neck, but 

 gets over the difficulty by keeping it upright. This no doubt 

 suggested the attitude given in Dr. Tornier' s restoration of the 

 skeleton. 



At first sight Diplodocus might possibly appear a somewhat 

 defenceless kind of animal, but judging from the habits of certain 

 living reptiles, such as the monitors, one may safely conclude that 

 this long tail was used very effectively as a whip whereby to lash its 

 enemies. Its great length is remarkable. The long neck doubtless 

 made a long tail desirable, otherwise Diplodocus could not succeed in 

 hitting an enemy trying to attack its head. 



Professor H. F. Osbornin his paper on " A. Skeleton of Diplodocus " 

 (on p. 14) leans to the view that Diplodocus was of aquatic habits, 

 holding that the tail was especially modified to function as a 

 swimming organ, and was provided distally with a vertical fin. He 

 believes the chief function of the tail to have been that of a pro- 

 peller to aid the animal in swimming, and that it functioned 

 secondarily as a balancing and supporting organ. While holding 

 that the Sauropoda are aquatic and quadrupedal, he infers that they 

 were capable of migration on land and assuming both a bipedal and 

 tripodal position, the tail when in the latter position functioning as 

 a third support in conjunction with the hinder pair of legs. 



