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ALLAN HANCOCK PACIFIC EXPEDITIONS 



VOL.2 



These 7 species are so closely similar to their Atlantic mates that they 

 might be considered by some as no more than varieties of the same species. 

 They probably correspond to the pairs of geminate species known in other 

 groups. Except in the case of Tetrochetus coryphaenae (which apparently 

 occurs in Coryphaena both at Tortugas and Japan) all of these species 

 are limited to the Atlantic or Pacific coast of America, and in the case 

 of every pair the fish hosts in the two oceans are closely related. The 7 

 Pacific species involved in these pairs were collected only from the Gala- 

 pagos Islands and not from the coast of the mainland. Furthermore, the 

 Atlantic representatives all occur in the warmer southern waters (all 

 being definitely known at Tortugas except L. kernostoma, which prob- 

 ably occurs there). Only B. plicatum also extends north to Woods Hole. 

 Only one (Lobatostoma) of the 7 genera is an endemic amphi-American 

 genus. Thus, these twin-species have somewhat the same complexion as 

 the identical and endemic species (Table 1) except that on the Pacific 

 side they seem to be restricted to the Galapagos Islands. Is this condition 

 more evidence of the species-stimulating isolation enjoyed there? 



TABLE 3 



Pacific Species with Nearest Related Species in the Atlantic but with 



Ordinary Specific Differences 



2. Leurodera pacifica 

 L. decora 



Anisotremus interruptus 



A. virginicus 

 Haetnulon plumieri 

 H. carbonarium 

 H. macrostomum 

 H. sciurus 

 H. flavolineatus 

 H. parra 

 Luiianiis griseus 



Galapagos Islands 

 Tortugas, Florida 



3. Opecoelina pacifica 

 O. scorpaenae 



Paralabrax species 

 Scorpaena cristulata 



Galapagos Islands 

 Tortugas, Florida 



4. Theletrum lissosomum 



T. fustiforme 



angelfish 



Pomacanthus arcuatus 



Socorro Island, 

 Mexico 



Tortugas, Florida 



