DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 35 



b. Dorsal short, posttnedian. Scales thin, caducous Paralepidid^ 



c. Dorsal short, median. Body naked Odoxtostomidjs 



** Vertebric normal. Anterior neural spines abnormally developed, projecting through the skin of the 



back, in advance of the dorsal. 

 1. Body compressed, ventradiform, carinated. 



a. Mouth obliiiuely cleft, or subvertical Stersoptyculd.e 



•** Vertebra; with spiny processes anteriorly which project through the skin of the back in front of dor- 

 sal rays. 



1. Pectorals absent. Body elongate. 



a. Body naked. Dorsal beginning in advance of the vent Idiacantiiid^ 



Family ALEPOCEPHALID^^. 



Alepocephales, Cuvier & Valexciexnes, Hist. Nat. Poiss., xix, 169. 



AlepoccphalicUr, Richardson, Encyc. Britannica, 8th td., 1856, 25.5. — Gt'XTHER, Cat. Fish. Brit. Mus., vii, 



1868,477. — Gill, Arrangement, Families of Fishes, 17. — Jordax and Gilbert, BuU. xvi, U. S. Nat. Mus., 



257. 

 Alepocephaloidei, Sleeker, Enum. Spec. Pise. Aich. lud., 1859, xxx. 



Malacopterygiaus with body more or Jess compressed, covered with thin cycloid or keeled 

 scales, or with naked, i)rickly skin. Head naked. I^o barbels. Month moderate or large, 

 the margin of the npiier jaw lormed by the premaxillaries and maxillaries, the former placed 

 along the upper anterior edge of the latter. Opercular apparatus complete. Teeth feeble. 

 No adipose fin. Dorsal fin long and low, posterior, inserted opposite the anal; pectorals 

 short, jjlaced rather high; veutrals usually well back, sometimes wanting. Pseudo- 

 branchiie present. No air bladder. Stomach curved, without blind sac. Pyloric cceca in 

 moderate number. Gill openings very wide. 



KEY TO THE GENERA OF ALEPOCEPHALID.^;. 



I. Body covered with scales. 



A. Ventrals present. 



1. MaxiUaries toothless; month of moderate width ; scales thin, cycloid. 



a. Dorsal and anal similar and nearly equal ; body oblong Alepocephalus 



b. Anal much longer than dorsal ; body elongate Conocara 



2. Maxillaries toothed; mouth wide. 



a. Gill openings narrow, teeth in premaxilla and mandible uniserial BATnYTROCTES 



b. GUI openings wide, teeth in premaxLUa and mandil)le pluriserial N.\rcetes 



B. Ventrals absent; scales small, keeled; body abbreviated, high, much comiiressed Platytroctes 



II. Body scaleless. 



A. Dorsal normal, equal in length to anal ; scales replaced liy nodules. 



1. Lateral line present Xenodermichthys 



2. Lateral line absent Aleposomus 



B. Dorsal normal, shorter than anal Leptoderma 



C. Dorsal preceded liy a long adipose fold A-XOMALOPTERUS 



III. Body with minute, hardly imbricate scales. 

 A. Pseudobranchiie quite rudimentary. 



1. Bones of the head i)roduced in a long snout Ailostomatomorpha 



ALEPOCEPHALUS, Risso. 



Alepocephalus, Eisso, Mem. Accad. Nat. Sci. Turin, xxv, 1820, 270. — Ml'ller, Abhandl. Akad. AViss. Berlin, 

 1846, 171.— CuviERand Valexciennes, Hist. Nat. Poiss., xix, 169.— GCxther, Cat. Fish. Brit. Mus., 

 VII, 477. — Jordan and Gilbert, Bull, xvi, U. S. Nat. Mus., 257. 



Body oblong, compressed. Mouth moderate, the snout somewhat prolonged. Jaws 

 nearly even in front; a scries of small teeth in each jaw and on the vomer and palatines. 

 Eye very large. Gill membranes entirely separate. Brauchiostegals 0. Opercular bones 

 thin. Dorsal low and rather long, with a scaly base, opposite and similar to the anal. Pec- 

 torals and ventrals rather small. Caudal moderately forked. Scales rather large, thin and 

 cycloid. 



