48 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



much greater thau lialf tlic diaiiieter of the eye. The veutral origin i.s ('(|uidista!it from the 

 posterior margin of tlie eyi; and the base of the posterior dorsal ray ; it is slender, and reaches 

 nearly, if not (luitc, to the vent. Color, uniform blackish. 



A single specinu'n (No. Xi5fA, U. S. N. M.), 3^ inches in length, was ol)tain(>d by tlie 

 AlbatroHS at station 2099 in 37° 12' 20" N. hit., 09° 39' W. Ion., at a depth of 2,9i9 fathoms. 



AiiErOSOMlS SOCIALIS, (Vaillant), Goodf, and Bean. (Figure 58.) 



Xenodcrmiohthiis aociaVis, Vaillant, Exj). Sci. Tiavaillcur et Talisnian, 1888, 162, pi. xni, fig. 1. 



Body compressed, with upper and lower outlines parallel for the gi-eater portion of their 

 length. Its length is nearly 6 times its height. 



Head one fourtli of length of body. Snout very short, hardly one-fourth length of the 

 head, while the mandible, which extends considerably beyond the upper jaw, is nearly lialf 

 as long as head. The maxillary reaches nearly to the line of the center of the eye. Small 

 teetli upon the mandible and premaxillary. The palatines, the tongue, and the idiaryngeal 

 bones are toothless. Tlie eye is encunuous, its diauieter two-fifths of the length of the head. 

 It protrudes above the profile, forming a protuberance noticeable either at the side or from 

 below. Width of interorl)ital space scarcely one-sixth of the length of the head. Gill 

 opening large, although the opercular slit does not reach very far up, its ui)per edge being 

 attached to the body by a membrane. 



In the fresli individual the skin was slimy, covered by a thick mucus, so that the lateral 

 line can not be distinguished; is doubtless UR'rged in the fold between the upi)er and lower 

 nuiscular masses. No trace of scales. Vent situated behind middle of body. 



The dorsal extends behind the caudal jieduucle ; it is not very high and is slightly raised 

 posteriorly in relation to the dorsal outline. The anal i-esembles it precisely in size and 

 shape; the caudal is deeply emarginate, and is }ueceded above and below by very distinct 

 accessory rays, which occupy half of the distance between the dorsal and the anal. The 

 paired tins are but little developed, short, and the pectorals have about IG rays. 



Color uniformly deep blackish, violet; the flns seem lighter ou account of their trans- 

 lucency. There are traces of black spots upon the membrane of the anal, and also under 

 the eye upon the cheek and the opercidar flap, and these continue also upon the belly; 

 these spots are more conspicuous in the specimen when it is preserved thau when it is fresh. 

 The iris is violet; pupil opaline. ( Vaillant.) 



This species was obtained in great abundance ou the Banc d'Arguin, where 133 specimens 

 were obtained in one haul, at a depth of 1,2.30 meters. It was also obtained in small numbers 

 off the coast of Morocco from 717 to 1,350 meters, and ou the coast of Soudan at 800 meters. 

 Vaillant seems to be somewhat uncertain whether or not this form beh)ugs to the genus 

 Xenodermichthys, and remarks that, comparing it with the diagnosis of Dr. Giiuther, he can 

 see nothing which absolutely rules it out. Assuredly, the skin presents no traces of rugosities 

 nor of any gi-owth which can be compared to scales eveu in a rudimentary condition. At all 

 events, it can be readily distinguished from Xcnoflcyiiiivhfht/s Ho^Z/z^o.v^.f of Giiuther, which 

 has an arrangement of fins very ditt'erent, and a much slighter development of the eye. 



As Vaillant says, the great abundance in which this fish was taken in one haul of the 

 deep-sea net would seem to indicate that it occurs in large schools in the depths of ocean. 



XenodermichthyH Giiiitheri, Alcock, Ann. and Mag. Nat. Hist., 1892, ii, 357, A^ol. 

 xviii, fig. 3, fiom Investigator, station 133, Indian Ocean, 078 fathoms, seems likely to 

 belong to this genus. 



LEPTODERMA, Vaillant. 



Leptoderma, Vaillant, Exp. Sci. Travailleur et Talisman, Poissons, 1888, 165. 



Body elongate, gradually diminishing posteriorly until it becomes almost thread-like. 

 Head moderate, but (in the only known species) with enormous eyes. Mouth small. Teeth 

 upon premaxillaries and maxillaries. A distinct submaxillary. Dorsal and anal elongate, 

 extended upon the caudal peduncle and ending slightly in advance of its extremity, the flns 

 very much larger than the dorsal. Gill opening wide, though not very liigh. No scales. 



