BY J. DOUGLAS OGILBY. 655 



by a preorbital space equalling or nearly equalling its diameter, 

 l>ut this appearance is deceptive and is caused by McCoy having 

 unfortunately figured both his examples with the premaxillary 

 extended to its fullest possible length, and given therefore a quite 

 erroneous idea of the aspect of the fish in its natural state, since 

 it is only under special conditions that the mouth is protruded 

 in the manner figured; this is also responsible for the wide space 

 between the termination of the premaxillary processes and the 

 origin of the dorsal fin. In neither of McCoy's specimens is the 

 height of the doi'sal rays so great as in ours nor is there any 

 mention made of spinules on the rays; the caudal fin is, however, 

 much longer and there is a distinct basal lobe; the pectoral fin is 

 much smaller, but is perhaps imperfect; in the larger example the 

 first ray of the ventral bears four spines in front near the base, 

 but in the smaller it is smooth as in our fish. 



Compared with arawatce the whole appearance of McCoy's 

 youngest specimen is so difii'erent that I have little hesitation in 

 pronouncing them distinct. 



Writing of the difficulties which confront the student in any 

 attempt to discriminate between the various forms of trachypterids 

 McCoy makes the following remarks : — 



" The relative length of the rays of the anterior portion of the 

 dorsal fin, the caudal fin, and the ventral fins in different 

 individuals is due to the excessive delicacy and fragility of the 

 rays — as fine as the finest hair and as brittle as spun glass —so 

 that the slightest touch in separating the rays to count them 

 l)reaks them in pieces. I think also that the young are deeper 

 and shorter in proportion than the old ; and, consequently, the 

 specific diff'erences founded on the greater number of times the 

 length of the head or the depth of the body are contained in the 

 total length are not to be trusted for specific characters when 

 the length of the specimens is different. I also believe the 

 numbers of rays in the dorsal fin increase with the length of the 

 body of the individual." 



"While agreeing that great alterations take place in the figure 

 of these fishes with increasing age, the labours of Emery and 



