THE DEEP-SEA FAUNA. 245 



Paxamiax. 



f G. willemoesii. S. of Amboiua in Bauda 

 Gnatliopliausia willemoesii (493-1270 fms.). -j Sea (1425 fms.). 



[ G. sarsii. Bay of Bengal (102 fms.)- 

 " brevispiuis (551-1471 fms.). Bay of Bengal (690-1748 fms.). 



Eucopia australis (551-1770 fms.). North aud Tropical Atlantic ; Southern 



Ocean ; Antarctic Ocean ; Japan ; Bay of 



Bengal ; Gulf of INIanaar (350-2500 fms.). 



Petalophthalmus pacificus (700 fms.). P. armiger. Tropical mid Atlantic (2500 



fms.). 



A study of the deep-sea Crustacea thus leads to the conclusion that this 

 fauna is one of cosmopolitan range, indivisible into subordinate local pro- 

 vinces like those of the littoral and terrestrial faunae. This is what one 

 would expect from tlie uniformity of conditions prevailing at great depths 

 and from the enormous length of time that has elapsed since modern types 

 of marine Invertebrata came into existence. We have seen not only that 

 many of the denizens of the cold waters of the intermediate zone, even with- 

 in the tropics, are emigrants from the shallow water of cold and cold-temper- 

 ate latitudes, but also that vei-y many of the peculiarly deep-sea tj'pes betray 

 their kinship with boreal genera. This, in the absence of much light from 

 paleontology in this particular group of animals, may afford us the clew to 

 the origin of a large part of the abyssal Crustacean fauna. Rarely, as in the 

 case of the recent Enjonticlcc, do we find a deep-sea tjpe that vividly recalls 

 an ancient form. In this case, so good an authority as Boas thinks that the 

 modern deep-water Polycheles is identical with the Jurassic Eryon. It is of 

 interest to note that in the same beds at Solenhofen — beds of undoubted 

 shallow-water origin — we find with Eryon another singularly antiquated type 

 in Limuhis. But the surviving descendants of Limiihis aie pre-eminently 

 littoral. It is manifestly illogical to assume, as some have done, that because 

 a certain form is now restricted to deep water the rocks in which it occurs 

 as a fossil were deposited at a similar depth. The surviving representatives 

 of an ancient shallow-water type may be littoral, as in the case of Limidus, 

 or they may be found only in deep water, like the recent Eryontidce. Some 

 unquestionably bottom-living species at the present day have a vertical 

 distribution of 2000 fathoms. For instance, Panqxigurus abysHorum ranges 

 from 250 to 2221 fathoms,* and Dall t states that certain species of Mollusca 



* Not taking into account the "Challenger" record of this species in 45 fathoms off Patagonia 

 (Henderson, Rep. Challenger Anoniura, p. 89, 1888). 

 t BuU. Mus. Comp. Zool., XII. 186, 1886. 



