234 DEEP SEA FISHES. 



Argyropelecus lychnus sp. n. 



Plate J, fig. 1,1b. 



Br. r. 9 ; D. VII + 9 ; A. 7 + 5 ; V. 6 ; P. 11. 



Very narrow and very deep in the body, half as deep and narrower in 

 the caudal section. Body cavity more than half of the total length, as also 

 is the greatest depth. In j'oung stages the depth is much less as compared 

 with the length. Length of the head about half of the depth of the body or 

 one third of the length from the snout to the caudal notch ; forehead very 

 narrow, with two longitudinal keels separated by a narrow groove, narrower 

 in the interorbital space. Eye large, less than half of the head. Snout 

 short, two thirds as long as the eye, blunt ; chin nearly vertical, with a 

 small symphyseal protuberance. Mouth wide ; maxillary twice as long as 

 the eye, forming rather more than half of the upper border of the mouth. 

 Teeth small, acicular, separated, in single series ; there are eleven or twelve 

 on the intermaxillary, of which the third or the fourth is the largest; there 

 are sixteen, more or less, on the maxillary, half of them hooking backward 

 and the posterior six or eight hooking forward ; the dentary teeth are 

 longer and erect, with the exception of a few of the anterior which are 

 hooked, the fifth or the sixth being decidedly so ; the few on the anterior 

 portions of the palatines are minute. Gill rakers long, half the length of the 

 eye, slender, eight (seven to nine) on the upper portion of the first arch 

 and eight to ten, with two or more rudiments, on the lower. A small spine 

 above each shoulder on the nape ; a spine below the preopercle ; another 

 less prominent below the angular. Ventral spine in two sections, of which 

 one turns forward, the other backward. Dorsal blade containing seven 

 spines, upper edge not denticulate. Anal fin in two divisions, indicated by 

 a larger interspace between the rays. Pyloric caeca six to seven or to five. 

 The blade in front of the dorsal fin, and the abdominal keel are not serrate. 



The lanterns, luminous organs, are distributed thus : one on the fore- 

 head ; one in front of and one behind the eye; two backward of the end of 

 the maxillary ; two above and backward from the base of tlie pectoral, and 

 six behind these, directly backward of the base of the fin ; and six in the 

 branchiostegal, six in the pectoral, twelve in the abdominal, four in the 

 ventral, six in the anal, and hwv in the subcaudal section of the lower or 

 ventral series. In these lanterns the disk is in the upper part while the 

 elongate lower portion is silvered as if for purpose of reflection. 



