36 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



KEY TO THE SPECIES OF ALEPOCEPHALUS. 



I. Opercular flaps voluminous; head large. 



A. Head one-third of total or nearly so. 



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



2. Scales moderate (67 in lat. line). Snout, 9 in body. Eye,4inhead A. productus 



3. Scales moderate (70 in lat. line). Snout lOiin body. Eye :U in head A. BLANFORDII 



I. .-•rail's small (about 90 in hit. line). Snout, 12 in body. Eye, 3J in head A. Agassizii 



B. Head less than one-third of total. 



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



I. Opercular flaps moderate ; bead moderate. 



1. Scales large (65 in lat. line). Snout 18 in body. Eye 4 i in bead .A. BAIRDIJ 



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



3. Scales large (50 in lat. line). Snout 18 in body. Eye 4+ in head A. edextui.us 



There are two distinct groups in Alepocephalus, probably of subgeneric value. The 

 first group includes the type. .1. rostratus, Eisso. It is characterized by a somewhat short, 

 compressed body, large head, with extended membranaceous flaps, and by short dorsal and 

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



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

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



A. Agassizii has somewhat smaller scales (about 90 in the lateral line), a comparatively 

 larger head (3 in total), and the eyes slightly larger (3A in head, 10£ in body). 



A. productus has a smaller eye than A. Agassizii, and a longer snout, it being about 

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

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



A. Blanfordii, Alcock (Ann. and Mag. Nat. Hist., 1S92, 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 aud 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 in A. Agassizii, etc., but with a smaller 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 

 their bases. Lateral line nearly straight. Mamillaries slender, not expanded posteriorly. 



A. bicolor, Alcock (Ann. and Mag., 1891, ii, 133), is from the Indian Ocean, 240-76 

 fathoms. 



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



ALEPOCEPHALUS ROSTRATUS, Risso. (Figure 41.) 



Alepocephalus rostratus, Risso, Mem. Aecad. Torin., xxv, 1820, 291, pi. x, fig. 4; Hist. Nat. del'Europe Meri- 

 dionale, 449, tig. 27. — Cuviek and Valenciennes, Hist. Nat. Poiss.. xix. 169, pi. 532. — JOHNSON, Ann. 

 and Mag. Nat. Hist., x. 1862, 285. — Gcnther, Cat. Fish. Brit. Mus., vn, 477. — Moreau, Hist. Nat. Poiss. 

 France, in. 463.— Gegenbattr, Morphol. Jahrbueh, iv. Snppl., 1, pi. 1, 2 (skull).— Gigi.ioi.i, Elenco, 

 1883, 106.— Vaillaxt, Exp. Sci. Trav. el Talisman, Poissons, 148, pi. XI, fig. 1; pi. xn, 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 of the dorsal tin opposite 

 to the vent. Pectoral fin longer than orbit. Distance of ventral lit t from the head three- 

 fifths the length of the latter. Uniform deep black. (Giinther.) 



Radial formula: B. 6; D. 16, 17; A. 18, 19; P. 13; Y. 8; L. lat. 55; Ccec pyl. 12. 



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

 Risso in 1S20. 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 off 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 Yerde Islands, 3,655 meters. Giinther 

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



