Fishes of the Western North Atlantic 481 



Generic Synonym: 



ParacentroscyHium Alcock, Ann. Mag. nat. Hist., (6) 4, 1889: 379; type species, P. ornatum Alcock, mono- 

 typic. Bay of Bengal. 



Generic Characters. Squalidae with well developed dorsal spines, their anterior edge 

 sharp, posterior flattened, each side with two shallow longitudinal furrows, originat- 

 ing at origins of fins and lying along anterior margins of latter, their tips well ex- 

 posed; trunk slender, subcylindrical; caudal peduncle with or without faintly marked 

 longitudinal dermal ridges and without precaudal pits; teeth (most distinctive generic 

 character) similar in the 2 jaws, with 3 to 5 cusps, the median much the largest; snout in 

 front of mouth shorter than from center of mouth to origin of pectorals; dermal denticles 

 thorn-like on stellate bases, or granular; eyes and spiracles large; nostrils oblique, their 

 anterior margins expanded as triangular lobes; mouth but little arched, a voluminous tri- 

 angular pit at corner of mouth extending as a short labial furrow on each jaw; posterior 

 margins of dorsals weakly concave, if at all so, the free rear corners not slenderly elongate; 

 origin of ist dorsal behind axil of pectoral; 2nd dorsal at least as large as ist, its origin 

 over or behind bases of pel vies; caudal with only weakly defined lower lobe, its axis raised 

 only a little; pectoral brush-shaped, its inner corner rounded and not at all produced; 

 some species, at least, with dermal thickenings that are presumably luminous. 



Range. North Atlantic; Falkland Islands; eastern tropical Pacific; vicinity of Ha- 

 waiian Islands; Japan; Indian Ocean, including Bay of Bengal and Arabian Gulf. 



Species. The few species so far known are deep-water forms from widely distributed 

 localities which closely resemble one another in general appearance and in their black or 

 very dark brown coloration. While closely allied, they appear sufficiently differentiated 

 from each other to deserve separate names. 



Key to Species' 



la. First dorsal spine over or in front of tips of pectorals when latter are laid back. 



2a. Tip of caudal truncate, with definite subterminal notch, nigrum Garman, 1899. 



Eastern Pacific off Panama; 

 near Galapagos Islands; near 

 Cocos Island and off Ha- 

 waiian Islands.^ 



2b. Tip of caudal pointed, without definite subterminal notch. 



* ornatum Klcock, 1889. 



Bay of Bengal and Arabian 

 Gulf.» 



1. Species marked * have not been seen by us. 



2. For list of references and localities of captures, see Fowler (Bull. U.S. nat. Mus., 100 [/j], 194.1 : 252) and Beebe 

 and Tee-Van (Zoologica, N. Y., 36, 1941: 120). 



3. It is probable that Burckhardt's (Ann. Mag. nat. Hist., [7] 6, 1900: 567, fig. 7) figure more nearly represents 

 the normal shape of the caudal than does Alcock's (111. Zool. "Investigator," 1894: pi. 8, fig. 3) original illus- 

 tration of it. For list of references, see Fowler (Bull. U.S. nat. Mus., 100 [z^], 1941 : 254). 



