394 ANNUAL. REPORT SMITHSONIAN INSTITUTION, 1923 



Sailors, no matter how callous they may be toward other forms of 

 life, quickly learn to recognize silicious sponges. 



The coelenterates are the only group of animals of which a large 

 proportion of the types are confined to deep water. They are 

 abundant here, and of many different sorts. Especially characteristic 

 are the sea-pens and umbellularians and the curious anemones. There 

 are many corals, largely solitary ones, but no massive types, and 

 numerous alcyonarians and allied creatures. 



Various sea squirts occur, both simple and compound. 



Crustaceans are abundant, of all the principal marine groups ex- 

 cept the king crabs and the squillas, though barnacles are poorly 

 represented. They are mostly blind and spiny. There are a few 

 sea spiders or pycnogonids, some of which are very large ; one single 

 kind lives all the way from the shore line down to 13,350 feet below 

 the surface. 



Mollusks of all the principal groups except the pelagic occur; one 

 type, called solenogaster, a wormlike thing living on gorgonians and 

 apparently parasitic on them, is most abundant in deep water. 

 The gastropods or snails, though there are no remarkable forms in 

 the deep sea, are interesting in ranging from at least 16,000 feet 

 below the surface uninterruptedly to above the snow line in the 

 Himalayas. 



The fishes are practically all of the bony or teleostean type, and 

 chiefly represent modifications of forms represented at or near the 

 surface in the cold and temperate zones, or which appear as nocturnal 

 oceanic forms. They are small, mostly black or dark sooty brown, 

 sometimes albinistic, blind or with large eyes, and often with long 

 filamentous processes. 



Of the remaining animals there may be mentioned the few brachio- 

 pods, less interesting geologically than the littoral ones, some sipun- 

 culids, the few annelid worms, mostly living in calcareous or quill- 

 like tubes, the numerous radiolarians, and the foraminifera. 



From this catalogue one might, perhaps gather the impression 

 that animal life in the abysses is abundant, which is far from true. 

 A net dragged for two or more hours over the sea floor, an operation 

 consuming almost an entire day, may bring up less than a handful 

 of animals, or even none at all. Rarely, and usually near shore off 

 precipitous coasts, are rich hauls made. 



Like their relatives in shallow water, the deep-sea animals, es- 

 pecially the echinoderms and sponges and pennatulids, tend to live in 

 colonies, with various crustaceans, worms, etc., associated with them. 

 Sometimes the dredge brings up only the dead remains of such a 

 colony which has died from the exhaustion of the meager food sup- 

 ply, or from old age or other cause. 



