26 THREE CRUISES OF THE " BLAKE." 



is covered by a flaccid, scaleless skin, is. toothless, and has its 

 head covered with a system of wide muciferous canals, the der- 

 mal bones being almost membranaceous. It is either a very 

 ancient or a very degenerate type, but bears a remarkable 

 superficial resemblance to its ally, Lucifuga, which inhabits the 

 subterranean waters of caves in Cuba, and has lost the use of 

 its eyes. 



The typical family of cods (GadidaB) is also numerously repre- 

 sented in the depths of the sea ; those forms which descend to 

 the greatest depths being usually of a more elongate form 

 than the brotulids, and with a small, often filamentous, first dor- 

 sal fin. 



The Ophidiidae (Ophidium cervinum] (Fig. 201) are elongated 

 Gadoids. 





Fig. 201. Ophidium cervinum. About 1. (U. S. F. C.) 



The Lycodidse are abundant in the polar waters and lesser 

 abysses of the North Atlantic and Pacific, and occur also where 

 the Atlantic abysses merge into the Antarctic. 



The macruroids (Fig. 202) are characteristic abyssal forms, 

 and both specifically and individually are exceedingly numerous 

 at all depths below the hundred-fathom line. Seventy-five per 

 cent at least of the fishes brought up in the trawl from the 

 abyssal regions are members of this family. Macrurus is rare 

 below 1,000 fathoms, only one species, M. Bairdii, having strag- 

 gled below this limit. It is more abundant inside the five hun- 

 dred-fathom line, and Steindachneria, a macruroid with a high 

 differentiated first anal fin, has been obtained by the " Alba- 

 tross " in 68 fathoms. The species and individuals of Coryphae- 

 noides and Bathygadus (Fig. 203) are as numerous below 500 

 fathoms as those of Macrurus are above it. The cavernous struc- 

 ture and membranous texture of their skeletons are very marked, 

 and they seem, through their elongate forms, tapering tails, im- 

 mense heads, and strongly armed bodies, to be especially adapted 



