Zoology.] NATURAL HISTORY OF VICTORIA. [F»Ae». 



distance from snout varying with protrusion of jaws ; greatest thickness of body, 

 about 2 lines (figured specimen). Second specimen — Length, 1 ft. 4 ins. 6 lines ; 

 greatest depth of body, 2 ins. 6 lines ; length of head (half protruded), 2 ins. 3 lines ; 

 height of middle of posterior dorsal, 1 in. 9 lines. 



Reference. — = (Bloch and Sch.), p. 480 = T. falx (Cuvier and Val.), Hist. 

 Pois. v. 10, p. 333; = ? T. iris (Cuv. and Val.), id. p. 341, t. 297. 



The fishes of this genus resemble silver ribands or bright sword- 

 blades, from their narrow, tapering, greatly compressed bodies, and 

 the glistening silver lustre of the nearly smooth, scaleless surface. 

 They are less known than those perhaps of any other genus, on 

 account not merely of their rarity, but from their inhabiting the 

 profound depths of the ocean, whence they rarely emerge, and 

 where they are not exposed to the rough motions of shallower 

 waters, in which they are quickly battered to pieces. The whole 

 structure is so frail, brittle, and delicate, and so easily and quickly 

 decomposed, that it is extremely difficult for observers to describe 

 them ; and I feel convinced that several of the described species are 

 really only differently observed individuals of one or two species. 

 Thus 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 breaks them in pieces. 

 I think also that the young are deeper and shorter in proportion 

 than the old ; and, consequently, the specific differences 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. I notice that Cuvier and 

 other observers of actual specimens invariably describe the largest 

 specimen as, proportionally, the longest and most slender, and with 

 the length of head or depth of body forming the least proportion 

 of the total length, while small specimens, an inch or two long, are 

 more ovate, with the head and the depth going fewer times in the 

 total length. I therefore think it very likely that the T. Spinolce 

 of Cuvier may be the young of his T. falx, and T. iris, and T. 

 taenia, to which I refer our Victorian species. The smaller 



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