DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 125 



length only 7 inillinieters. Also the relative position of the luminous organs, which are 

 congregated in groups, is subject to unimportant variations. 

 Two forms are recognized by Giinther: 



(1) In the first and more common (Fig. D) the eye is comparatively larger and its 

 diameter more than the depth of the triangular space, which is formed by the margins of 

 the preoperculum, of the jaws, and of the orbit; the upper part of the mouth is also con- 

 spicuously above the level of the lower margin of the orbit. 



(2) In the second form (Fig. D') the diameter of the eye is not longer than the depth of 

 the triangular space described, and the upper part ol the cleft of tlie mouth is on a level 

 with the lower margin of the orbit. 



Both forms occur in the Indo-Pacific as well as Atlantic, and seem sometimes to have 

 been obtained on the same occasion; and as, moreover, intermediate forms occiu' which 

 might be assigned to either of the two forms, it is evident that the differences mentioned 

 are not of specific value. 



Very young specimens, of 1~> millimeters in length, were found by Giinther already to 

 possess all the characteristics of the adult. 



Specimens of this species were taken by the Blake, from Station xxxv, off' Santa Cruz, 

 at a depth of .508 fathoms; from Station cccxxiii, in 33o 19' N. lat., 70° 12' 30" W. Ion., at 

 a depth of iol fathoms; and from Station CCCXVI, in 32° 7' N. lat., 78° 37' 30" W. Ion., at a 

 depth of 229 fathoms. Also by the Albatross ft'om the following localities: Cat. No. 32008, 

 U. S. N. M., from station 2003," in 37° 10' .30" N. lat., 74° 20' .36" W. Ion., at a depth of 641 

 fathoms; cat. No. 33471, U. S. N. M., from station 2070, in 41° 13' N. lat., 66° 00' M" \V. 

 Ion., at a depth of 906 fathoms; cat. No. 33503, U. S. N. M., from station 2101, in 39° 18' 

 30" N. lat., 68° 24' W. Ion., at a depth of 1686 fathoms; also specimens from station 2111 

 in 350 09' 50" N. lat., 74° 57' 40 W. Ion., at a depth of 938 fathoms; station 2118 in 13° 32' 

 40" N. lat., 620 54' W. Ion., at a debth of 690 fathoms; station 3553 in 39° 48' N. lat., 70° 36' 

 W. Ion., at a depth of 551 fathoms; and station 2.554 in 39° 48' 30" N. lat., 70° 40' 30" W. 

 Ion., at a depth of 445 fathoms. A single specimen (Cat. No. 26235, U. S. N. M.) was taken 

 by the schooner Guy Ciinningliam off the Grand Bank at a depth of 150 fathoms. 



Ur. Giinther, after studying the specimens obtained during the voyage of the Challenger, 

 reached the conclusion that its frequent capture at all dej)ths from surface downward is 

 only a proof of its abundance in all tropical seas, and of the slowness of its movements, 

 which prevent it from getting out of the way of the dredge or net. He infers that, like 

 Argyropelecns, it is a i)elagic fish, which probably lives in shoals, as sometimes more than 

 one example were obtained in the same haul, and that possibly it may descend to or beyond 

 the 100 fathom line during the daytime. More information is needed upon all these 

 points. 



ARGYROPELECUS, Cocco. 



Argyropelccus, CocCO, Giorn. Sci. Sicil., 1829, fasc. 77, 146; Cuvier ami Valenciennes, Hist. Nat. Poiss., 



xxii, 392. — Gi'NTiiSR, Cat. Fish. Brit. Miis., v, 389; Challenger Report, xxil, 167. 

 Pleuroihyris, Lowe, Fish. Madeira, 64. 



Trunk much elevated and compressed, passing abruptly into the tail, which is nairow; 

 body covered with a silvery pigment, without regular scales; series of luminous (phosphor- 

 escent) spots run along the lower side of the head, body, and tail. Head large, compi'essed, 

 and elevated, with the bones thin, but ossified. Clei"t of the mouth wide, with the lower 

 jaw prominent. The margin of the upper jaw is formed by the intermaxillary and max- 

 illary, both of these bones having a sharp edge, which is beset with a single series of 

 minute teeth; lower jaw and palatine bones with a siuies of small, curved teeth. Eyes 

 rather large, and, although lateral, directed upward and very close together. Pectorals 

 well developed, ventrals very small. The Ininieral arch and the pubic bones are prolonged 

 into fiat, pointed iirocesses, which project in the median line of the belly; a series of imbri- 

 cate scutes runs from the humeral to the ])ubic bone, forming a sort of serrature along the 

 belly. The dorsal fin is short and occupies about the middle of the length of the fish; it 

 is preceded by the first commencement of the formation of a spinous dorsal, several neural 



