208 THE VOYAGE OF H.M.S. CHALLENGER. 



Opostomias, n. gen. 



This genus differs from Echiostoma by its dentition, the long teeth not being 

 depressible, but received in grooves or hollows of the opposite jaw. Maxillary and 

 palatine teeth absent. A barbel. 



Opostomias micripnus (PI. LIII. fig. A). 



Echiostoma micripnus, Giinth., Ann. and Mag. Nat. Hist., 1878, vol. ii. p. 180; Narr. Chall. 

 Exp., vol. i. p. 412. 



B. 15. D. 21. A. 23. P. 1 I 3. V. 7. 



The length of the head is nearly one-ninth of the total (with the caudal). Barbel 

 much longer than the head and fringed at its extremity ; the anterior pectoral ray 

 filamentous and distinctly separated from the others. Boot of the ventral rather nearer 

 to the extremity of the snout than to the root of the caudal. Black ; luminous organ 

 above the maxillary small, round, like a rudimentary eye. 



Habitat. — South of Australia, Station 159; depth, 2150 fathoms. One specimen, 

 15^^- inches long. 



The height of the body is one-eighth of the total length, the length of the head two- 

 ninths. Head moderately compressed ; interorbital space convex, broad, its width being 

 contained twice and two-thirds in the length of the head. Cleft of the mouth wide, but 

 not quite extending to the angle of the prseoperculum, the posterior margin of which is 

 vertical. Gill-cover completely covering the gill-cavity, narrow. Eye small, half as long 

 as the snout and one-sixth or one-seventh ' of the length of the head. 



Jaws armed with very strong teeth, few in number and not depressible. About one- 

 half of the length of the upper jaw is formed by the intermaxillaiy and the other half 

 by the maxillary. The intermaxillary bears four teeth, of which the second is by far 

 the strongest and received in a shallow impression behind the large fang of the mandible. 

 The three other teeth are subequal and of rather small size. Maxillary toothless. 

 Mandible broad and deep, armed anteriorly with two large and pointed fangs, which are 

 distant from each other and are received in a deep hollow of the upper jaw. This 

 large mandibulary fang is succeeded by three teeth only, which are remote from each 

 other and somewhat larger than the opposite teeth of the upper jaw. Vomer with a 

 small fang on each side. Palatines toothless ; upper pharyngeals with some small 



fangs. 



Pupil of the eye vertical. Nostrils close together, above the eye, on the upper surface 

 ^ The eyes are not exactly of the same size on each side. 



