Cope.] 438 [May 19, 



from Tresca's " flow ;" Clarke's two estimates accord more nearly with the 

 theoretical value ; while Listing's, which is the latest of ail, gives an agree- 

 ment which is virtually exact. If we start from his estimate (1 : 288.4), 



4-2 X 288.4 

 Ave get <i — (•g(ji(j4 i)i 1' = 32.086 ft. Ganot's value is 32.088 ft. It can 



hardly be believed that sucli a coincidence is merely accidental. If it is 

 indicative, as I have supposed, of inter-molecular jEthereal action, it has an 

 important bearing on tidal equilibrium, and it shows that Earth's shape 

 and rigidit}'- were not fi.\ed in any past age, but are at all times adjusted 

 to the requirements of internal elasticity and external attractions. Any 

 arguments which may be adduced in favor of such an adjustment may be 

 urged, a fortiori, in support of the flow and thrust of a plastic material 

 like ice. The velocity of terrestrial rotation, in the mean latitude which 

 Prof. II. C. Lewis has indicated for the terminal moraine in Pennsylvania, 

 is more than 1000 feet per second. The centrifugal force consequent upon 

 such a velocity, together with the thrust of an ice-cap which extended to 

 the pole, must greatly facilitate glacial flow. The equilibrating forces 

 would work upon local gfaciers, in the same way as upon a general 

 ice-cap. 



The Classification of the Uivjulate Mammalia. By E. B. Cope. 

 {Read hcfove the American Philosophical Society, May 19, 1882.') 



In the present essay the osseous system is chiefly considered, and of this, 

 the structure of the feet more than of any other part of the skeleton. The 

 iingulata are here understood to be the hoofed placental Mammalia with 

 enamel covered t^eth, as distinguished from the unguiculate or clawed 

 and the mutilate or flipper limbed, and the edentate or euamelless, groups. 

 The exact circumscription and definition is not here attempted, though 

 probably the brain furnishes an additional basis of it in the absence of the 

 crucial, parietooccipital, calparine fissures, etc. Suffice it to say that it is on 

 the whole a rather homogeneous body of mammalia, especially distin- 

 guished as to its economy bj-- the absence of forms accustomed to an 

 insectivorous and carnivorous diet, and embracing the great majority of 

 the herbivorous types of the world. 



The internal relations of this vast division are readily determined by 

 reference to the characters of the teeth and feet, as well as other less im- 

 portant poyits. I have always insisted that the place of first importance 

 should be given to the feet, and the discover}' of various extinct types has 

 justified this view. The predominant significance of this part of the 

 skeleton was first appreciated by Owen, who defined the orders Perisso- 



