450 THE GENERAL PRINCIPLES OF ZOOLOGY 



The Protozoa are here represented by a number of the Rhizop- 

 oda, some of which attain a considerable size, such as Hypcram- 

 mina elongata, which grows to a length of fifteen millimeters. 

 The most conspicuous and characteristic deep-sea sponges are 

 the siliceous sponges, such as the Venus' flower basket, Eu- 

 plcctclla, and the genus Hyalonema, then a few medusae, sea 

 anemones, and corals. All classes of the Echinodermata are 

 richly represented, the stalked Crinoidea being notably abun- 

 dant. Of the worms there are a few Bryozoa and Brachiopoda, 

 and a number of tube-forming Chaetopoda. Curious Crustacea 

 are found there, a few barnacles, some gigantic Isopoda, 

 thirty centimeters long, Schizopoda and Uecapoda of odd 

 shapes ; there are several species of long-legged spicier crabs, 

 often of considerable size, as the Lithodes agassizii, whose cara- 

 pace is about fifteen centimeters in diameter, while with legs 

 extended it measures a meter from tip to tip. The Pycnogonida 

 have some large representatives, one species having an expanse 

 of sixty centimeters when the legs are extended. The Mollusca 

 are not numerous ; there are several species of Cephalopoda, 

 and the giant squids occasionally cast up on the shore are doubt- 

 less deep-sea animals living along the slopes of the continental 

 shelf. Finally, there are numerous fishes. It must be noted 

 that many littoral and pelagic fishes can descend to consider- 

 able depths, some undertaking seasonal migrations ; hence many 

 families of surface fishes have been taken at depths between 

 200 and 1000 meters ; only two or three extend to 1400 meters, 

 and two or three to 2000 and 4000 meters. There are over 

 thirty families of deep-sea fishes known which never occur in 

 water less than 2000 meters deep. These are Teleostei, and 

 many of them are grotesquely specialized, having enormous 

 mouths, or excessively long teeth, or tactile organs developed 

 out of all proportion to the rest of the body ; many are phos- 

 phorescent either over the entire body, or in spots, especially on 

 the head. The "ribbon fishes," Regalecus, occasionally east 

 ashore, are probably deep-sea types, although they have never 

 been dredged from the depths ; we have already called attention 

 to them in Chapter IX as probably responsible for some sea- 

 serpent fables. Few Selachii have as yet been discovered in 

 the deep sea. 



