DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 113 



size; only 3 remain on each side of the intermaxilla. The maxilla has 20 true teeth on its 

 anterior half, and the posterior half has about 16 serrse. There arc about 35 teeth on each 

 side of the mandible. All the teeth of the jaws rake inward and backward, and are 

 depressible. Three teeth on each side of tlie head of the vomer, increasing in size back- 

 wards. A pair of teeth on each palatine bone. One fang near- the tip of the tongue and 

 3 farther back. Four gills, a small slit behiud the fourth. The gill lamina? not well cov- 

 ered by the operculum. Gill rakers very few, minute, and spine-like. Gill opening very 

 Avide, the membrane cleft almost down to the origin of the hyoid barbel. No pseudo- 

 branchiffi. The hyoid barbel is situated nearly under the tip of the tongue; it is evidently 

 imx^erfect, its length being scarcely one-half that of the eye. 



The length of the head (20 millimeters) is contained Si times in length to base of cau- 

 dal. The origin of the dorsal is at a distance from the caudal base (44 millimeters), a little 

 more than one-fourth of the standard length. The length of the dorsal base (34 milli- 

 meters) is one-fifth of the standard length. The longest dorsal ray is a little longer than 

 the eye. 



The anal begins immediately under the dorsal, and its base is slightly longer than that 

 of the dorsal; its rays are about as long as those of the dorsal. The distance from the end 

 of the anal to the origin of the middle caudal rays (10 millimeters) equals one-half the 

 length of the head. The distance of the ventral from the tip of the snout (87 millimeters) 

 is a little more than one-half of the standard length; consequently the origin of the 

 ventral is very slightly nearer to the root of the caudal than the tip of the snout. The 

 distance from the origin of the ventral to that of the anal slightly exceeds the length of 

 the anal base. Caudal and ventral imperfect. Pectoral wanting. 



Eadial formula: D. 18; A. 21; V. 7; P. 0. 



Color, very dark. A row of luminous dots along the margin of the branchiostegal 

 membrane; two rows lieginning on the isthmus and extending back along the edge of the 

 belly, passing between the ventrals and slightly above the base of the anal, disappearing 

 near the end of the body ; another row higher up on the side, which cannot be traced back 

 farther than the origin of the ventral, on account of the bad condition of the specimen. 



This specimen was obtained by the steamer Blake, at station XL, off Martinique, in 

 472 fathoms. 



Family MALACOSTEID^E. 



Malacosteidre, GiLL, Arr. Families of Fishes. 



Body elongate, compressed, scaleless. Mouth immense. Snout very short. Cleft of 

 the mouth exceedingly wide, the ends of the jaws extending beyond the root of the pectorals, 

 and the jaws not connected with the sides of the head back of the orbit. Tail diphycercal. 

 Lateral margins of the upper jaw formed by the intermaxillaries only. No adipose fin. 

 No barbel. Pectorals rudimentary. 



PROVISIONAL KEY TO THE GENERA. 



A. Pectorals present Malacosteus 



B. Pectorals absent. 



1. Palatines smooth Photostomias 



2. Palatines toothed Tiiaumastomias 



MALACOSTEUS, Ayres. 

 MaJaeoste.us, Ayres, Jonrn. Bost. Soc. Nat. Hist., 1849. 53.— GCnthf.r, Cat. Fish. Brit. Mus., v, 428. 



Body elongate, compressed, scaleless. Head rather compressed, the snout very short, 

 the cleft of the mouth very wide, extending to behind the root of the pectorals. Teeth 

 pointed, unequal, in single series on both jaws and tongue; none on the palate. Opercula 

 membranaceous. Dorsal far back, op])osite anal. Pectorals rudimentary. Ventrals rather 

 posterior. No barbel. {Ayres, Jordan and Gilbert.) 

 19868— No. 2 8 



