hatcher; diplodocus (marsh) 59 



Sauropoda as constituted on the roesaxonic plan, and in the present restoration that 

 plan has been followed entirely upon the authority of Osborn. There is, indeed, a 

 striking contrast between the supposed mesaxonic arrangement in the manus and 

 the entaxonic arrangement that is known to obtain in the pes. Nevertheless Os- 

 born has shown that there are some very strong evidences in favor of such an arrange- 

 ment in the fore feet, and strikingly different as would then be the structure of the 

 fore and hind feet, yet it would be no more striking that wdiich is known to prevail 

 among certain recent sloths in the Mammalia. 



The most striking features brought out by the present restoration are the ridicu- 

 lously short dorsolumbar region and the exceedingly small size of the skull and an- 

 terior cervicals when compared with the great length and size of the animal. The 

 abbreviation of the dorsolumbar region is accomplished both by the reduced num- 

 ber of dorsals and by the shortening of the centra of the individual vertebrae of 

 this region. While in the caudal and cervical regions length is gained both by an 

 increase in the number and in the length of the individual vertebrae in either 

 series, in the caudal series length is gained chiefly by increasing the number of ver- 

 tebrae, while the cervical region owes its elongation for the most part to the great 

 length of the individual vertebrae, especially in the posterior and mid-cervical re- 

 gions, though the number of cervicals is also considerable, not less than fifteen. 



Probable Habits of Diplodocus. 

 As first noted by Professor Marsh, the position of the narial opening at the apex 

 of the cranium in Diplodocus is indicative of aquatic habits. Moreover, the extreme 

 modifications of the limb bones, vertebrae, and, indeed, of all the larger bones of 

 the skeleton, whereby the greatest possible area for muscular attachment is afforded 

 with the least possible increase in weight, are adaptations admirably calculated to 

 increase very considerably the buoyancy of so massive an animal when in water. 

 The deeply pitted articular surfaces of the various parts of the appendicular skele- 

 ton are perhaps indicative of thick cartilaginous pads interposed between such sur- 

 faces at the various joints of the limbs and feet. This want of closely fitting and 

 well-defined articular surfaces would appear to afford additional evidence in favor 

 of aquatic habits, and that the movements of the animal when on land were de- 

 cidedly slow and clumsy, for had Diplodocus and its ancestors been addicted to ter- 

 restrial life the habitual support of so massive a body in so light a medium as the 

 atmosphere would scarcely have failed to produce closely applied and well-finished 

 articular surfaces, similar to those which obtain in such members of the Theropoda 

 as are of undoubted terrestrial habits. From the above consideration I am inclined 



