FISHES. — MCCULLOCH. 115 



Type. — Cyttosoma verrucosa in, Gilchrist, var. propinquus, 

 var. uov. 



Boulenger 1 considers that Cyttosoma verrucosum is possibly 

 the adult form of Oreosoma, Cuvier & Valenciennes 2 , and if his 

 view is correct, the above genus is unnecessary. There are. 

 however, several important differences between Allocyttus 

 (Cyttosoma) verrucosus and 0. atlanticitm, which seem to me to 

 indicate that they are not generically identical, though closely 

 related. 



0. atlanticum was, until recently, known from only a few very 

 small examples, but Waite 3 has lately described and figured a 

 New Zealand specimen 80 mm, long, which does not differ in its 

 essential characters from the smaller ones. Though there is a 

 great difference in size between my smallest specimen of 

 Allocyttus, 253 mm., and Waite's example, it is nevertheless 

 difficult to suppose that a fish could undergo such a remarkable 

 change of form as would be necessary to alter it from Oreosoma 

 to Allocyttus, particularly as it retains its larval characters 

 unchanged up to a length of 80 mm. Oreosoma has a stout body 

 which is trigonal in section, while Allocyttus is compressed. The 

 large conical tubercles of the small fish are altogether differently 

 arranged to the flat scales which are supposed to represent them 

 in Allocyttus, the lower ones being below the ventral fins. None 

 of the scales are imbricate in Oreosoma, but are six-sided 

 and form a mosaic, whereas only a portion of them are so 

 arranged in Allocyttus, the remainder being imbricate. 



I therefore believe that the unknown adult form of Oreosoma 

 will prove to be generically distinct from Cyttosoma verrucosum. 

 and therefore propose Allocyttus for the latter. It differs from 

 Cyttosoma and Pseudocyttus in having vomerine teeth and ctenoid, 

 adherent scales, while the structure of the scales separates it 

 from Neocyttus. These genera may be readily distinguished by 

 the following key :— 



a. No vomerine teeth. Scales deciduous, cycloid, or with 

 minute soft points. 

 b. Some enlarged flat scales below the origin of the dorsal 

 aud on the sides of the abdomen. Back abruptly 

 elevated behind the head. Preorbital very 

 narrow Cyttosoma. 



1 Bouleuger — Oompt Rendu Acad. Sci. Paris, cxxxvii., 1903, p. 523. 



2 Cuvier & Valenciennes — Hist. Nat. Poiss., iv., 1829, p. 515, pi. xcix. 



3 Waite— Trans. N.Z. lust., xliv., 1912, p. 197, pi. xi. 



