266 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



Gills 3i or 4; slit behind the last gill small, or obsolete; gill-rakers short, tubercle-like, or 

 obsolete; gill-membranes broadly connected, often joined to the isthmus. Body naked, or 

 with scales, prickles, or plates, but never uniformly scaled. Lateral line simple. Dorsal 

 fins separate or somewhat connected, the spines less than thirteen in number, usually slen 

 der, the soft part elongate, longer than spinous portion; caudal rounded; anal similar to 

 soft dorsal, spineless; pectorals large, with broad, procurrent bases; ventrals thoracic 

 (rarely entirely wanting), the rays usually less than i, 5. Pseudobranchiae present, at least 

 in all our species. Pyloric cseca usually in small number (4-8); air-bladder commonly 

 wanting. 



KEY TO THE DEEP-SEA GENEEA. 



I. Spinous dorsal not concealed. 



A. Gill openings extending below at least to the base of the lowest pectoral ray COTTIN.E 



1. Slit behind last gill obsolete. 



a. Gill membranes free from isthmus, or else forming a broad fold across it; head well armed. 



Palatines toothless. No true scales on body G'ottus 



Palatines with well-developed teeth. Body more or less scaly. 

 Upper preopercular spine hooked, bifurcate. 



Body with some scales or plates Icelus 



Body naked Artediellus 



Upper preopercular spine with 3-5 hooked processes Icelinl'8 



2. Slit behind last gill evident. 

 Palatines toothless. 



Gill membranes free from isthmus; series of plates along back and along lateral line. 



No plates on head; space between lateral plates prickly Tkiglops 



Plates on snout and opereles Prionistius, Bean = PAi>ruxrs, Gilbert 



II. Spinous-dorsal little developed, continuous with soft dorsal, the spines slender, concealed in the loose 



nakedskin; gill membranes broadly joined to isthmus; no slit behind last gill Psychrolutin.e 



A. Vomer and palatines toothless Psychrolutes 



B. Vomer with teeth. 



1. Gill membranes attached to isthmus. 



a. Teeth on vomer and palatines. Dorsal continuous Cottunculus 



6. No teeth on vomer and palatines. Dorsal in two parts Maxacocottus 



2. Gill membranes free from isthmus. 



«. Vomerine teeth in two patches, none on palatines. Dorsal in two parts [Dasycottus] 



COTTUS, Linnaeus. 



Coitus, Linn.eus, Syst. Nat. Ed., x, 1758, i, 207, ed. 2, 1766, 1,451.— GI'nther, Cat. Fish. Brit.Mus. n, 155 — 



Jordan and Gilbert, Bull, xvi, U. S. Nat. Mus., 700. 

 Acanthocottus, Girard, Smithsonian Contributions to Knowledge, in, 1858. 



Cottids with body rather slender, subfusiform, covered with thick skin, in which are 

 sometimes embedded prickly plates, especially along lateral line: deciduous granular tuber- 

 cles also sometimes present, but no true scales. Head large. Mouth terminal, large, the 

 lower jaw included; villiform teeth on the jaws and vomer, none on the palatines; sub- 

 orbital stay strong; preopercle with 2 strong straight spines above, directed backward, and 

 1 below, directed downward and forward; opercle, nasal bones, orbital, rim, and shoulder 

 girdle usually armed; gill membranes forming a fold across the rather narrow isthmus; slit 

 behind last gill small or wanting, often reduced to a mere pore; vertebra} about 28. Branehi- 

 ostegals mostly 6. Dorsal fins 2, separate, the first short, its spines rather slender; ven- 

 tral rays usually I, 3. — (Jordan and Gilbert.) 



Several species of this genus are found at a depth of 10 to 15 fathoms on c ir Xew England 

 coast. None have, however, been taken below the 100-fathom line, saving C. bathybius, 

 Giinther, from south of Yeddo, Japan. 



ICELUS, Kroyer. 



Icelus, KrOyer, Naturhist. Tidsskr., I, 253, 1844 (type, Icelus hamatns, Kroyer).— GCntiier, Cat. Fish. Brit. 

 Mus., n, 172.— Jordan and Gilbert. Bull, xvi, U. S. Nat. Mus , 689. 



Cottids with body fusiform, covered with rough scales or plates. Mouth rather large; 

 teeth on vomer and palatines. Head naked, usually with cirri; preopercular spine hooked, 



