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



substance ; and it appears that there is a large patch of similar substance in the gill- 

 cavity on and in front of the clavicle. 



The entire specimen is black, the vertical fins of a somewhat lighter colour; the upper 

 central rays of the caudal black. Ventrals whitish, the hind part of the three inner rays 

 black. 



Mr. Murray ^ observes : — " The end of the barbel, which was thickened, was flesh 

 colour with a rose tint, there was also a rose tint on the dorsal and anal fins. The rest 

 of the animal was of a dark colour with a perceptible slate-coloured tint. The phosphor- 

 escent spots along the belly and lateral line were red, as was also that below the eye," 



Pachystomias, n. gen. 



This genus diflFers from Echiostoma by the absence of a separate pectoral ray; also by 

 a much less developed dentition, vomerine and maxillary teeth being absent, 



Pachystomias microdon (PI. LIII. fig. C), 



Echiostoma microdon, Giintli., Ann. and Mag. Nat. Hist., 1878, vol. ii. p. 180. 



D. 24. A. 29. P. 3. V. 7. 



The length of the head is more than one-fifth of the total (with the caudal). No 

 separate pectoral ray ; root of the ventral considerably nearer to the base of the caudal 

 than to the extremity of the snout. All the teeth rather small, a few only in the middle 

 of the palatine bone. Black ; two luminous organs below the eye, a narrow elongate 

 one above the maxillary, and a small short one nearer to the eye. 



Habitat. — North-West of Australia, Station 181 ; depth, 2440 fathoms. One 

 specimen, 9 inches long, 



* This fish is a much shorter and heavier fish than Echiostoma harhatum, somewhat 

 approaching Malacosteus in its physiognomy. The head and body are compressed ; the 

 greatest depth, immediately behind the head, is one-fifth of the total length, the length 

 of the head two-ninths. The head is enveloped in rather thick skin, like the body, well 

 hiding the underlying parts. Upper part of the head rather short, cleft of the mouth 

 exceedingly wide, extending backwards nearly to the margin of the gill-opening; the 

 prseopercular edge is therefore very oblique. Interorbital space convex, but with a 

 depression along the middle caused by two longitudinal ridges ; its width equals the 

 diameter of the eye, which is as long as the snout, and one-fourth of that of the 

 head. Nostrils close together, round, lateral, in front of the eye. Snout rounded, 



'Narr. Chall. Exp., vol. i. p. 412. 



