REPORT ON THE PELAGIC FISHES. 27 



of moderate lengtli, embracing a considerable part of the tail, the rudimentary rays 

 advancing far forward on the upper and lower sides of the tail. 



The pectoral fin is inserted in the middle of the side, asymmetrical, many-rayed, as 

 long as the head. The ventral fins (c) are inserted at some distance from each other ; their 

 base is very small, and each is composed of two very slender rays, the longer of which 

 reaches beyond the vent. 



The scales are lost but to judge from the folds of the skin they must have been 

 extremely thin and very small. 



The entire fish is uniformly silvery. 



A young specimen (PI. III. fig. D), 19 mm. long, obtained on the 15th of September 

 1873, indicates the presence of another species in the Pacific, but as the specific characters 

 in this genus evidently change with age, I hesitate to introduce it with a distinct specific 

 name. It seems to have a smaller eye than the other species ; the ventral fins are two- 

 rayed but much stronger than in Auchenoceros punctatiLS ; the anterior dorsal ray is 

 placed opposite to the operculum ; the long dorsal and anal fins commence opposite to each 

 other ; they are not divided into separate portions and continuous with the caudal fin ; 

 but this is probably only a sign of young age. 



Fierasfer acus, Briinn., young (PI. IV. fig. F). 



In the year 1860, Kaup^ described a small fish in the British Museum as the type of 

 a new genus, Porohronchus. T. Gill * alludes to it in these words : — " As to Porohron- 

 chus, Kaup, it is, perhaps, related to Fierasfer ; but the character of the first elongated 

 dorsal ray requires to be known before a decision can be arrived at ;" whilst I ' stated it to 

 be the , young of Fierasfer acus. It is 2^ inches long and not in a good state of pre- 

 servation. A very similar fish, probably of the same species, was examined by Gasco * 

 who published almost simultaneously with my observation a description and figure of it, 

 considering it to be the type of a new genus, Vexillifer. His specimen was 20 mm. 

 long and re-examined by Costa ° who adopted Gasco's nomenclature. However, some 

 years later, Emery " confirmed my view as to the nature of this fish, from an examina- 

 tion of very young examples which are undoubtedly Fierasfer acus. 



The most conspicuous characteristic of these young Fierasfer is the presence of an 

 extremely long anterior dorsal ray which bears a variable number of small skinny lobes. 

 As the fish grows, this ray is lost or shortened by absorption. The specimens observed 

 by the Italian naturalists showed this ray more or less completely developed, whilst 

 in Kaup's specimen the greater part of the ray and every trace of the lobes had dis- 



^Ann. and Mag. Nat. Hist, 1860, ser. 3, vol. vi. p. 272, pi. iii. fig. D. 



2 Aym. aiid Mag. Nat. Hist., 1865, ser. 3, vol. xv. p. 48. 3 Catal. Fish., vol. viii. p. 145, 1870. 



* Bull. Assoc. Natur. e Med. Napoli, 1870, April, p. 59, c. tab. 



s Ann. Mus. Zool. Napoli, vi., 1871, p. 88, tav. 2, fig. 1. 



« Atti Sac. Ital. Sci. Nat., xxi. 1878, p. 37, figs. 1-3; and Atli R. Accad. d. Lincei, 1879-80, vol. vii. tav. 1, a. 



