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



But the most extraordinary change takes place in the position of the vent. In young 

 specimens (of 12 inches and less) the vent is placed between the ventrals (fig. a), 

 immediately behind their roots at some distance from the origin of the anal, and the 

 distance between vent and isthmus is only about half the length of the head. In the 

 adult, in which the abdominal organs are fully developed, the external extent of the 

 abdomen is also enlarged, the vent being moved backwards behind the ventrals 

 immediately in front of the anal, and the distance between vent and isthmus has been 

 much increased, being equal to the length of the head. 



* 



Macrui'us nasutus (PI. XXX. fig. B). 



Coryphsenoides nasutus, Giintli., Ann. and Mag. Nat. Hist., 1877, vol. xx. p. 440. 

 Allied to Macrurus mdis. 



D. 12 I 95. A. 110. B. 20. V. 10. 



Snout obtusely conical, witli a rather sharp upper edge, and with a more or less pro- 

 jecting knob in the middle. The snout projects beyond the mouth, the cleft of which 

 does not reach to below the middle of the eye The teeth of the outer series are scarcely 

 stronger than the remainder. Barbel very small. The width of the interorbital space is 

 not quite equal to the vertical diameter of the eye, w^hich, in a specimen 14 inches long, 

 is nearly one -fourth of the length of the head, and equal to that of the snout. Tlie 

 structure of the scales is almost identical with tliat in Macrurus ritdis. They are 

 equally rough over the whole of their surface, the spinelets being subequal in size, densely 

 packed, and not arranged in scries. The majority of these spinelets are strengthened by 

 a strong longitudinal keel (fig. h). There are seven or eight scales in a transverse series 

 between the first dorsal and the lateral line. Second dorsal spine somewhat produced, 

 armed along its anterior edge with barbs pointing upwards and rather closely set. The 

 second dorsal fin commences at a considerable distance behind the first, the distance being 

 nearly equal to the length of the head. The outer ventral ray produced into a filament, 

 shorter than the fin. 



Ilahitat. — South of Ycddo, Station 235; depth, 565 fathoms. Five specimens, 

 14^ and 14 inches long. 



7/?/a/onema-ground, off Inosima, Japan, Station 232 ; depth, 345 fathoms. Six 

 specimens, about 12 and 13 inches long. 



Tlie number of dorsal and anal rays must always be sul)ject to cousiderabh; variation, 

 because the end of the tail is not equally produced in all individuals. In several specimens 

 the tail has been mutilated at an early stage of growth, and in such cases the truncated 

 stump is surrounded by a rayed fin, very mucli of the same appearance as the caudal fin 

 of the ordinary Teleostean type. 



