88 TILREE CRUISES OF THE " BLAKE." , 



Pselopatides (Fig. 346) and Ankyroderma ^ (Fig. 347) seem 



t ■f *> . 



Fig. 346. — Paelopatides confundens. |. (Th^el.) 



to be the only typical truly deep-sea genera of the orders of 



Apoda and Pedata collected 



by the " Blake," not before 



'f^T ^^^ found in the littoral regions, 



^ ^ while the other deep-sea spe- 



^^"^^t^l^ ^^ cies belonging to genera found 



Fig. 347. — Ankyrodermaaffine. |. in sliallow watcr are merely 



(Koren & Danielssen.) '£11 J' j.' j. £ i.1 



^ speciiically distmct irom the 



littoral forms, though undoubtedly, like other marine animals 

 capable, of living at extreme depths, they have become accus- 

 tomed to their different conditions of existence most gradually, 

 and those which live in deep water have acquired characters and 

 habits somewhat distinct from those dwelling in the more lit- 

 toral regions, but which a close study alone would reveal. 



SEA-URCHINS. 



One of the most common sea-urchins is Dorocidaris jxtpil- 

 lata (Fig. 348), a type having a very wide geographical distribu- 

 tion ; it is found everywhere in the Atlantic, and has even been 

 dredged in the Pacific ; it came up in the dredge often to the 

 exclusion of all other forms. It recalls a cretaceous type common 

 both in Europe and America. As in all the Cidaridse, the shape, 

 proportions, and ornamentation of the spines vary greatly, and 

 an exaggerated importance has frequently been assigned to char- 



1 Ankyroderma affine when alive is of a grayish color, the integument is thin, and 

 the extremities of a lighter hue than the body. 



