4o8 DA VI SON. [Vol. XI. 



musculature should exist, and the required processes for the 

 many attachments. The conical arrangement of fibres in the 

 dorsal muscle reveals a condition quite the opposite of degener- 

 ation. The fact that similar muscular cones are found in the 

 alligator (13) and SpJiaenodon does not imply that these three 

 forms are in any way related. The existence of an unusually 

 long and strong temporo-cervical tendon in Amphiuma and 

 DcsviognatJms does not furnish sufficient evidence that they 

 are closely allied, as Cope has tabulated them. These are 

 merely cases of parallelism, as is plainly shown when we 

 take into consideration the marked contrast of the more im- 

 portant structural elements of the two families. Scott (19) has 

 demonstrated this condition of parallelism in numerous mam- 

 malian families. " The prismatic, cement-covered molar has 

 been independently developed in many forms : e.g., several 

 of the ruminants, certain pigs, the horses, one of the rhi- 

 noceroses (Elasmotherium), the elephants, many rodents, etc. 

 The selenodont molar pattern has been several times inde- 

 pendently evolved ; (i) in the true ruminants ; (2) in the camels; 

 (3) in the oreodonts. The spout-shaped odontoid process of 

 the axis has arisen in the true ruminants, the horses, the cam- 

 els, and, to a certain degree, in the later oreodonts, such as 

 Merychyus." Gegenbaur (20) [p. 669, Fig. 232] has described 

 and figured incorrectly the muscular arrangement in the tail of 

 the fish. The wall of the cone is incomplete adjacent to the 

 spinal column, in all the fish which I have examined. This 

 tendency toward conical arrangement of fibres in the tail of 

 the fish has been evolved by the same mechanical principles 

 that obtain in Amphiuma. Thus it may be noticed that in 

 many respects AmpJdtima is not a degenerate form, but on 

 the contrary possesses highly developed structures; and were 

 it not for the fact that the brain exhibits such primitive char- 

 acters [Osborn (8), p. 178], I would consider this type the 

 result of progressive rather than retrogressive evolution. 



