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



The scales are somewhat differently sculptured on the different parts of the body of 

 the fish, in individuals of different ages, and in specimens from different localities. In a 

 specimen from the Kermadec Islands, 23 inches long, a scale (fig. a), taken from the 

 middle of the fish above the lateral line, has from five to seven nearly parallel ridges, of 

 which the middle one is the highest, ending behind in a strong spine. The other ridges 

 are more or less faint, with small spines either at the end or in the middle. In the scales on 

 the back (fig. a'), as well as on the abdominal region, the median spine projects strongly and 

 is preceded by two or three smaller ones, which cover each other in an imbricate fashion. 

 In the scales of the lateral line the median ridge is, as it were, longitudinally divided 

 by the muciferous channel, forming above and below the line a series of imbricate spines, 

 Generally no other ridges being visible on these scales. On the head the scales are more 

 or less modified into scutes, with serrated ridges, which form more or less regular stellate 

 figures on each scute, rendering the whole surface of the head very rough ; the largest 

 scutes are those occupying the raised bony ridges which are found in every species of 

 this genus. The course of the muciferous channels on the snout and other parts of the 

 head can be easily traced by series of very small and short black tubules, by which the 

 mucous secretion is discharged, and which are particularly numerous on the lower part of 

 the snout. 



In a specimen from the Kermadec Islands, which is only 12 inches long, all the spinous 

 projections are comparatively weaker and the parallel ridges on the scales less distinct. 



In a New Zealand specimen, 18|- inches long, the dermal ossifications on the 

 head are considerably smaller, so much so that they do not always touch each 

 other; also on the body the spines project less, but the parallel arrangement of the 

 ridges is much more conspicuous. On the other hand, in Japanese specimens the arma- 

 ture is much more developed, and there is not the same great difference in the size of 

 the median and lateral spines. 



In a young specimen 5^ inches long from Japan (fig. A') the snout has already 

 the characteristic form and is nearly twice as long as the eye, the body is scaled, and on 

 some of the scales (fig. a") minute spines are arranged in two or three series, but not 

 close enough to form continuous ridges. No scutes are visible on the head except 

 along the osseous ridges found in nearly all the species of this genus. 



Very young specimens (fig. A"), 2^ inches long, are partially covered with extremely 

 delicate scales (fig. a'"), those on the back being armed with a stronger median 

 and sometimes an additional pair of weaker lateral spines. The ridges on the head are 

 simply serrated and the snout is comparatively shorter, the eye being only two-thirds of 

 its length. 



Figures A of PI. XXIX. represent the entire view of a specimen from the Kermadec 

 Islands, and the lower view of its head, of nearly two-thirds of the natural size ; A', side 

 view of the head of a young Japanese specimen (5^ inches long); A", a very young 



