PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 359 



curred in most of the deeper dredgiiigs. Large quantities of a large, 

 handsome, but very fragile, cup-coral {Flabcllum Goodei V.) occurred in 

 the deeper localities, esi^ecially at stations 880, 894, 895, but most of the 

 specimens were ruined by being crushed by the great weight of the 

 contents of the trawl. The animal of this coral is bright orange, with 

 a purple center. 



While many of the species of every class obtained here are arctic, or 

 belong to the cold Avaters found at similar or greater depths on the coasts 

 of Europe and in the Mediterranean, a few genera, like Avicula, Solarium, 

 and Marginella, are related to southern or West Indian forms. A num- 

 ber of the most abundant species of Crustacea and Echinoderms* had 

 already been described from the collections made bj' Pourtales, off 

 Florida. 



Many free-swimming species, belonging to the Pteropoda and Hete- 

 ropoda, of which we dredged the dead but perfectly fresh shells, were 

 not previously known to occur so far north. They were associated with 

 others of the same groups which had previously been taken living at the 

 surface along our shores, but they all belong jiroperly to the Gulf Stream 

 fauna. 



The frequent occurrence of nearly fresh shells of Argonauta Argo was 

 also a matter of surprise to us, and indicates that this species must 

 often be very common near our coast. 



The very large collections of specimens obtained on these three trips 

 have, as yet, been only partially examined, but enough has already been 

 done to prove this region to be altogether the richest and most remark- 

 able dredging ground ever discovered on our coast. The large number 

 of new forms, combined with others jireviously known only from remote 

 regions, constitute a very distinct fauna, hitherto almost wholly un- 

 known. 



A considerable number of undetermined, and perhaps undescribed, 

 shells from these localities are not included iu this article. 



* A brief accouut of the Echiuoderms obtained, by us, with descriptions of several of 

 the new species discovered, has been x>ublished by me in the Amei'icau Journal of 

 Science for November, 1880. 



It is only necessary to say here that several of the star-tishes, Ophiurans, and Crin- 

 oids occurred iu such large numbers as to constitute one of the most conspicuous 

 features of the fauna. The most abundant species were Archaster Americanus V., A. 

 Affassizii V., A. Florw V., Luidia elegavs Perri^r, OpMocnida olivacea Lym., Ophioscolex 

 glaciaViH ]\I. & Tr., Ojjhiotjh/plM Sdrsii Lym., Antedon Sarsii (D. & Koren). 



All these species, except the last two, are orange-colored, varying to orange-red. 

 The same is true oi Acanella Normam, of most of the Actinians, and of the majority of 

 the crabs and shrimps, as well as of some of the fishes. It seems probable that the 

 prevalence of orange and red colors among the deep-water animals is due to the fact 

 that the luminous rays of those colors are completely absorbed by the thick, overlying 

 stratum of sea-water, and consequently these animals, not being capable of reflecting 

 such bluish and greenish rays as do reach them, would be nearly invisible at those 

 depths beyond which white light penetrates. If this be true, such colors, being jiro- 

 tective, may be due to the operation of natural selection, according to the principle 

 so often exemijlified in shallow-water animals having colors like their surroundings. 



