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THE AMEBIC AN NATURALIST [Vol. XL V 



lus shown me by Dr. L. Stejneger has the thickness of the 

 body only .57 of the height ; so that it is nearly as much 

 compressed as Dr. Holland has represented Diplodocus to 

 be. Various other genera of lizards include species with 

 much compressed bodies. Some of the tortoises belong- 

 ing to the genus Testudo have the shell about twice as 

 wide as high, while in T. abingdonii, from the Galapagos 

 Islands the shell is fully as high as wide. Nevertheless, 

 this tortoise shows no tendency to assume a mammalian 

 gait. I see no reason why, if the necessities of the ani- 

 mal required it, the shell might not, in the course of time, 

 become still higher. 



It is of great value to have, from one so competent as 

 Dr. W. D. Matthew, a statement regarding the value to 

 be attached to the form of the femur in relation to the 

 pose of the sauropods. Dr. Matthew seems to agree 

 with me that straightness alone of the femur does not 

 prove that these animals walked erect on either two or 

 four legs, only, he appears to hold that the larger mam- 

 mals and dinosaurs have in general straighter femora 

 than their smaller and more agile ancestors. This state- 

 ment is, of course, subject to the condition that the femur 

 was not straight in the ancestors themselves. And when 

 we come to apply the statement to the dinosaurs we are 

 likely to dispute whether the femora of Tyrannosaurus 

 are or are not less curved than those of some earlier 

 dinosaurs. Dr. Matthew describes the hinder limb of the 

 elephant and asserts that all gigantic mammals show 

 some approach to this type; also, that in the sauropods 

 the resemblance in form and proportion of the hinder 

 limb to that of the elephant is very marked. However, 

 a number of the genera that he mentions as illustrating 

 his views seem to me not to conform well to the specifi- 

 cations. Titanotherium does not, if we may rely on the 

 restorations, 4 have post-like legs nor, in comparison 

 with the elephant, short feet. Coryphodon does not have 

 straight legs, 5 nor is it a gigantic mammal, being ex- 



'** Am *r- Mus. Nat. Hist., VII, pis. VIII, X, XI. 

 8 Bull. Amer. Mus. Nat. Hist., X, pi. X. 



