DISCUSSION OP SPECIES AND THEIR DISTKIHCTION. 125 



length only 7 niillimeters. Also the relative position of the luniinons organs, which are 

 congregated in groups, is subject to unimportant variations. 

 Two forms are recognized by Giintlier: 



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

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

 the preoperculum, of the jaws, and of the orbit; the n})per 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 dei)tli of 

 the triangular space described, and the upper part of tlie cleft of the 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 occur which 

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

 are not of specific value. 



Very yoxmg specimens, of lo millimeters in length, were found by Giintlier already to 

 possess all the characteristics of the ailult. 



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

 at a depth of uOS fathoms; fiom Station CCCXXIII, in 33'^ 19' N. lat., 70° 12' 30" W. Ion., at 

 a depth of 4.J7 fathoms; and from Statitm cccxvi, in 32° 7' N. lat., 78° 37' 30" W. Ion., at a 

 depth of 22!) fathoms. Also Ijy the Alhatross fi'om the following localities: Cat. No. 32t3(iS, 

 U. S. N. M., from station 2003,' in 37° 16' 30" N. lat., 74° 20' 3li" W. Ion., at a depth of 041 

 fathoms; cat. No. 33471, U. S. N. M.,fiom station 2070, in 41° 13' N. lat., 66° 00' 50" W. 

 Ion., at a depth of 000 fathoms; cat. No. 33.'')(!3, U. S. N. M., from station 2101, in 39° IS' 

 30" N. lat., 68° 24' W. Ion., at a depth of 1080 fathoms; also specimens from station 2111 

 in 35° 09' 50" N. lat., 74° 57' 40 W. Ion., at a depth of 938 fathoms; station 2118 in 13° 32' 

 40" N. lat., (i2o 54' W. hm., at a debth of (390 fathoms; station .35.53 in 39° 48' N.lat., 70O3(>' 

 W. Ion., at a depth of 551 fathoms; and station 2554 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 Gvy Cunningham, off the Grand l?ank at a depth of 150 fathoms. 



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

 reached the conclusion that its frequent capture at all depths 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 

 Aryyropdecm, it is a pelagic 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.Soi. Sicil., 1829, fasc. 77, 14(i; Cuvikr ami Valf.xciexxes, Hist. Nat. Poiss., 



XXII, 392.— GiixTHEE, Cat. Fish. Brit. Mus., v, 3S9; Clialleiiger Kepoit, xxii, 1G7. 

 Pleurothyris, Lowe, Fish. Madeira, 64. 



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

 body covered with a silvery pigment, without regular scales; series of luiuinous (ithosphor- 

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

 and elevated, with the bones thin, but ossified. Cleft of the month wide, with the lower 

 jaw prominent. The margin of the ni)per 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 iialatine bones with a series of small, curved teeth. E.ves 

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

 well developed, ventrals very small. The humeral arch and the pubic bones are jnolonged 

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

 cate scutes runs from the humeral to the ])nbic bon(>, foniiing a sort of serratnre along the 

 belly. The dorsal fin is short and occupies about the middle of tlie U-iigth of the fish; it 

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



