614 TELEOSTEI CHAP. 
definite one, and it has been used for the division of these Fishes 
into genera or sub-genera.’ The ventral fins have a more forward 
position than in most other members of the Family. 
Fam. 7. Alepidosauridae.—Characters as in the preceding, 
but supratemporal simple, attached to the opisthotic, and dorsal 
fin very long, formed of slender, non-articulated, simple or bifid 
rays, extending along nearly the whole length of the back, 
followed by a small adipose fin. The air-bladder is absent and 
the body scaleless. The skeleton is feebly ossified ; the dentition 
is very powerful, some of the teeth on the palate and mandible 
being very strongly enlarged. 4 or 5 species are known, from 
considerable depths in the Atlantic and Pacific Oceans, referable 
to one genus, Alepidosaurus or Plagyodus. A. ferox, from the 
Atlantic, reaches a length of 4 feet. 
Fic. 372.—Alepidosaurus ferox, + nat. size. (After Goode and Bean.) 
Fam. 8. Cetomimidae.—The affinities of the recently dis- 
covered genera Rondeletia and Cetomimus, deep-sea Fishes from 
the North Atlantic, at depths of 1000 to 1600 fathoms, are still 
uncertain, as the skeleton could not be examined; they are 
probably most nearly related to the Scopelidae. The head is 
enormous, with very wide gape, that of Cetomimus being 
suggestive of that of a Right Whale; the teeth are small and 
coarsely granular ; the gill-openings are very wide; the body is more 
or less compressed and scaleless; the dorsal and anal fins are 
opposed to each other; no adipose dorsal fin. In Rondeletia, the 
eyes are moderately large, and ventral fins, with 5 rays, are present; 
in Cetomimus, the eyes are very small, and ventral fins are absent. 
1 Cf. Raffaele, Mitth. Zool. Stat. Neap. ix. 1889, p. 179; Liitken, ‘‘Spolia 
Atlantica,” ii. 1892 ; Goode and Bean, ‘‘ Ocean. Ichthyol.” p. 70 (1895). 
