2 OLIVER P. HAY 



in an arc of a circle; further, that the feet were entaxonic, that is, had 

 the inner digits more strongly developed than the outer ones. 



Now, it is the writer's opinion that these evidences of digitigrady 

 will hardly stand a test. The hinder feet of the bear are certainly 

 plantigrade and yet the metatarsals are arranged very distinctly in 

 an arc of a circle. On the other hand, the tiger and the hyaena are 

 digitigrade, but their metatarsals are almost in a plane. Various 

 animals will, I think, be found to transgress Dr. Abel's rule, as one 

 may see by looking through a collection of skeletons. Furthermore, 

 if it is desired to see an entaxonic foot in which the metatarsals are 

 arranged in an arc of a circle and which is nevertheless plantigrade 

 one has only to examine the foot of the human skeleton. 



FIG. I SECTION THROUGH HIND FOOT OF TESTUDO. XL 05^, ASTRAGALUS; W^f. 

 2, METATARSUS OP SECOND DIGIT; ph. T, ph. 2, FIRST AND SECOND PHALANGES; 

 t., TARSAL OF SECOND ROW; tib., TIBIA. 



The writer is not disposed to deny that Diplodocus and its relatives 

 were more or less digitigrade; but this digitigrady, through perhaps 

 equal to that of the hinder foot of the elephant, does not prove that 

 these reptiles walked like the elephant. The land tortoises of the 

 genus Testudo have the feet constructed much like those of the elephant, 

 being provided with a thick pad of skin, muscles, tendons, and con- 

 nective tissue under the astragalus and the metatarsals and applying 

 only the ungual phalanges to the ground. Nevertheless the legs of 

 these reptiles stand out from the sides of the body as I have supposed 

 that those of Diplodocus did. A figure (Fig. i) is here presented 

 showing a section made through the hind foot of T. tahulata. Unfor- 

 tunately I have not been able to find or make a similar section through 



