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 (Gadidæ) 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 Ophidiide (Ophidium cervinum) (Fig. 201) are elongated 
Gadoids. 
Fig. 201. — Ophidium cervinum. About}. (U.S. F. C.) 
The Lycodide 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 Coryphe- 
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 
