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THE AMERICA.X XA TV 11 MA >i 



[Vol. L 



Lepidopus and its confreres are a foreign intermediate 

 family between the mackerels and Trichiurus, as Larus 

 domimcensis is a foreign intermediate species between 

 the two closely related types of black-backed gnll in the 

 north. Please note another analogy. The fundamental 

 philogenic Scombroid characters of Lepidopus are a 

 direct response to life at the surface of the mackerel 

 group. Though an intermediate it is impossible (as it is 

 difficult in Larus dominicensis) to believe that it occupies 

 the primitive habitat of the group. Other fishes which 

 have persisted in regions distant from the center of 

 ichthyological competition, namely the marine shore line, 

 as in the deep sea or in fresh waters, are in a sense foreign 

 intermediates. Before leaving Trichiurus let us glance 

 at its ancestry. The deep-sea Lepidopus-like fishes 

 would have little chance in competition with the 

 mackerels in surface waters. They form in a sense a 

 rectigradation (again apologies to Paleontology) de- 

 velopment from the mackerels of which Trichiurus is the 

 terminal member; but Trichiurus is so unmackerel-like 

 that it may and does inhabit the same waters with the 

 mackerels; it is broadly speaking complementary to 

 them. 



The tree squirrels are connected with the ground in- 

 habiting spermophiles through the chipmunks (Eu- 

 tamias, T ami as and Callospermophilus). Our common 

 eastern chipmunk (Tamias) is a boldly marked animal 

 in appearance very much resembling the Rock Squirrel 

 (Callospermophilus) of high altitudes of the northwest. 

 The resemblance is more striking than the closeness of 

 blood relationship would presuppose, and Callosper- 

 mophilus may be characterized in this connection as an 

 outcrop. The forms of Eutamias inhabiting the same 

 regions as Callospermophilus and sometimes found asso- 

 ciated with it, are very unlike that animal, and form a 

 very good complement with it, The eastern chipmunk is 

 a foreign intermediate in superficial characters between 

 Callospermophilus and western Eutamias. Interlocking 



