36 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



KEY TO THE SPECIES OF ALEPOCEPHALUS. 



I. Opercular flaps voluminous ; head large. 



A. Head oue-tbird of total or nearly so. 



1. Scales large (50-55, in lat. line). Snout, 10 in body length. Eye, 3} in head A. ijostratcs 



2. Scales moderate (67 in lat. line). Snout, 9 iu body. Eye, 4 in head A. iMtouicns 



3. Scales moderate (70 in lat. line). Snout lOi in body. Eye 3+ in head A. Bl.\nf()R1>ii 



4. Scales small (about 90 in lat. line). Snout, 12 iu body. Eye, 3i in head A. Ac.as.si/.ii 



B. Headless than one-third of total. 



1. Scales very .small (about 140 in lat. line). Snout, 10 in total. Eye 6 in bead A. xuiKl; 



1. Opercular flaps moderate; head moderate. 



1. Scales large (65 iu lat. line). Snont 18 in body. Eye 4J iu head A. BAiitnii 



2. Scales large (62 iu lat. line). Snout 15 in body. Eye 6 in head A. bicolou 



3. Scales large (.50 iu lat. line). Snont 18 in body. Eye U in head A. edentulus 



There are two distiuct groups in Alcpoctjjhahis, probably of subgeneric value. The 

 first group includes the type, A. rostratns, Eisso. It is characterized by a somewhat short, 

 compressed body, large head, with exteuded uiembrauaceous flaps, and by short dorsal and 

 anal fins, similar iu size and shape and nearly opposite each other. 



A. roKtratus has the largest scales, 50 to 55 in the lateral line (Vaillant claims to have 

 counted 71 on a large individual), and has a comparatively large eye and snout. 



A. Agassi^ii has somewhat smaller scales (about 00 in the lateral line), a comparatively 

 larger head (3 in total), and the eyes slightly larger (3J in head, 10| in body). 



A. 2>fo(hict)is has a smaller eye than A. Af/assizii, and a longer snout, it being about 

 one-third of the length of the head. In ^4. rostratus, however, the snout length is one- 

 tenth of the total; in A. productus one-twelfth. 



A. BlanforcJii, Alcock (Ann. and Mag. Nat. Hist., 1892, ii, 357), from the Indian Ocean, 

 has an immense eye. 



A. niger of Giinther is a somewhat slenderer form, with very small scales. 



All of these forms are dull in color and have the ventral fins weak and inconspicuous. 



A. Bairdii represents another type, having a stout body, about as high in proportion to 

 its length as iu A. Agassizii, etc., but with a snialler head and less voluminous opercular flaps 

 The eye is comparatively much smaller (18 in total length), and is nearer the upper profile 

 of the head. The vertical fins are stronger and more muscular, and are heavily scaled at 

 then- bases. Lateral line nearly straight. Maxillaries slender, not expanded posteiiorly. 



A. bicolor, Alcock (Ann. and Mag., 1891, ii, 133), is from the Indian Ocean, l.'40-7G 

 fathoms. 



A. edentulus, Alcock, I. c. is from the Indian Ocean, 475 fathoms. 



ALEPOCEPHALUS KOSTEATUS, Ei.sso. (Figure 41.) 



Alepocejihnhis roslraiux, Risso, Mem. Accad. Torin., xxv, 1820, 291, pi. x, fig. 4; Hist. Nat. de I'Enrope M^ri- 

 dionale, 449, fig. 27. — CuviEit .and Valenciennes, Hist. Nat. Poiss., xix, 169, pi. 532. — JonxsoN, Ann. 

 and Mag. N.at. Hi.st., x, 1862, 285.— GCnther, Cat. Fish. Brit. Mus., vii, 477.— Moreav, Hist. Nat. Poiss. 

 France, lu, 463.— Gegenbaur, Morphol. Jahrbuch, iv, Suppl., 1, jd. 1, 2 (sknll).— Giglioli, Elenco, 

 1883, 106.— Vaillant, Exp. Sci. Trav. et Talisman, Poissons, 148, pi. xi, tig. 1 ; pi. xii, fig. 5. 



The height of the body is a little more than one-fifth of the total length (without caudal) ; 

 the length of the head is a little less than one-third. Diameter of the eye contained thrice 

 and one-fourth in the length of the head, and longer than the snout. Scales much longer 

 than wide, with the anterior (radical) margin truncated. Origin ol' the dorsal fin opposite 

 to the vent. Pectoral fin longer than orbit. Distance of ventral fin Ironi the head three- 

 fifths the length of the latter. Uniform deep black. (G-ihiiher.) 



Eadial formula: B. 6; D. 10, 17; A. 18, 19; P. 13; V. 8; h. lat. 55; Ccec. pyl. 12. 



This species occurs in the deeper waters of the Mediterranean, and was described by 

 Eisso in 1820. Until 1874, when the Challenger began her work, this was the only repre- 

 sentative of the family known to ichthyology. 



The French expedition obtained twenty-four .specimens from ofl' the coasts of Soudan 

 and Morocco, from about 830 to 2,190 meters, from the Banc d'Arguin ; from the Canaries, 

 975 meters; the Azores, 2,235 meters, and the Cape Ycrde Islands, 3,655 meters. Giinther 

 is disposed to believe that Esunculus Costai is the young of this species. 



