24 THE VOYAGE OF H.M.S. CHALLENGER. 



Brcgmaceros atlanticus. Six specimens, the largest nearly 50 mm. long, were obtained 

 by the " Blake," at depths varying from 90 to 305 fathoms. This occurrence, taken 

 together with the facts that the Challenger obtained a young specimen in the open sea in 

 the Pacific, that Bregmaceros macclcUandii has a black-coloured pharynx, and that Brcy- 

 maceros macdellandii and Bregmaceros punctatus possess deeply sculptured cranial bones 

 with wide muciferous cavities, proves that these fishes inhabit the open sea, and descend 

 to considerable depths, although they seem not rarely to be met with close to the shore. 



I have mentioned above that I agree now with Mr. Hutton in regarding the New 

 Zealand form as the type of a distinct genus ; Mr. Hutton adopted the second generic 

 name given to Bregmaceros macdellandii, Calloptilum, for the genus which he 

 established for the New Zealand fish, but according to a generally accepted rule of 

 nomenclature, "this course is not admissible, and a new name has to be given to the latter. 

 It is not possible at present to determine to which of the two genera the young specimens 

 obtained by the Challenger and "Blake" should be referred. The dorsal and anal fins 

 are but little diff"erentiated in the young of all these species, and the structure and changes 

 of their ventral fins are very imperfectly known. 



I proceed first to give the distinctive characteristics of the two genera : — 



Bregmaceros, ThomT^s. = Calloptilum, ^\ch.=Ast7ienunts, Tick. 



Body fusiform, compressed posteriorly, covered with cycloid scales of moderate size. 

 Two dorsal fins, the anterior reduced to a single long ray on the occiput; the second and 

 the anal more or less depressed in the middle, in adult specimens the middle rays 

 becoming more or less obsolete, so that the fin appears to be divided into two. Ventral 

 fins well developed, composed of five rays, the three outer of which are dilated and much 

 elongated. Minute teeth in the jaws and on the vomer. Air-bladder large. Pyloric 

 appendages few in number (two). Gill openings very wide, the gill membranes being 

 united below the throat, and not attached to the isthmus. Pseudobranchise none. 

 Branchiostesrals seven. 



-o' 



Aiichenoceros, Gt\u: = Calloptil>nii, Hutt. nee Rich. 



Head and body compressed, elongate, covered with small, exceedingly delicate and 

 deciduous scales. Two dorsal fins, the anterior reduced to a single long ray on the neck, 

 above the pectoral ; the second more or less depressed in the middle ; one anal. Ventral 

 fins rudimentary, each composed of two slender elongate rays. Minute teeth in the jaws, 

 none on the vomer. Air-bladder small. Pyloric appendages in moderate number (eight). 

 Gill openings very wide, the gill membranes not being attached to the isthmus. Pseudo- 

 branchiae none. 



