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



Bregmaceros (PL III. figs. A-D). 



The progress of our knowledge of this genus has been somewhat chequered. It was 

 first described by William Thompson in Charlesworth (Ann. and Mag. Nat. Hist., 1840, 

 vol. iv. p. 184) from materials given to him by Cantor, viz., a young specimen 3 inches 

 long, and a drawing which, with some serious imperfections, was reproduced as a 

 woodcut to illustrate Thompson's description. The species was named Bregmaceros 

 maccIeUandii, and the genus recognised as a member of the family of Gadoids. 



Ignorant of the existence of this paper, Sir J. Richardson redescribed and figured 

 the same fish in the Voy. Sulphur, Ichthyoh (1843), p. 94, pi. xlvi. figs. 4-7, as 

 Calloptilum minim ; and, although a much better figure was given by him, his descrip- 

 tion leaves as much to be desired as that by Thompson, owing to the small size of his 

 examples, of which the largest was only 27 inches long, and is still preserved in the 

 British Museum. He difi'ered from Thompson in referring the genus to the Blennioid 

 fishes. 



Before comparing the descriptions given by these two zoologists, I must mention 

 that Richardson himself in 1856 recognised the generic identity of the two fishes 

 (Encycl. Brit., ed. 8, voL xii. p. 309), although he considered the species figured by him 

 to be distinct from that described by Thompson. He also added to the generic diagnosis 

 two apparently important characters, viz., the absence of caeca and of an air-hladcler. 



In 1862 I characterised the genus in the Catalogue of Fishes (vol. iv. p. 368) 

 chiefly after Richardson, having no other material beside that used bj' my predecessor, 

 and that considerably deteriorated. I diftered from him, however, in adopting 

 Thomj)son's views as regards the natural aflinities of the genus, in giving different 

 numbers of the fin-rays and scales, and, finally, in considering his Calloiitilum mirum 

 to be the same species as Bregmaceros maccleUandii. My reasons for taking this 

 latter view were, and are, the following : — 



The different statements made by the authors as regards the number of dorsal and 

 anal rays are to be accounted for by the uncertainty of the number of short and 

 rudimentary rays in the middle of those fins. In some specimens it is impossible, and 

 in all very difiicult, to ascertain their number ; nor is there such a marked break 

 in the formation of the fin, that one could say exactly with which ray the anterior 

 division ends and with which the posterior begins.' The difficulties are, of course, the 

 greater, the smaller the specimens ; thus, Richardson gave in the small specimen, which 

 he figured, thirteen as the number of rays composing the posterior dorsal, whilst I 

 count fifteen or sixteen in the same specimen, and up to twenty in others. Similar 



' lu my diagnosis I have, therefore, expressed this uncertainty by the mathematical sjonbol x, which by some 

 subsec[uent writers has been coijied as the roman figure X. 



