OCR Text |
Show 1866.] MR. J. Y. JOHNSON ON TRACHICHTHYS DARWINII. 315 from T. australis, Shaw, it may be distinguished, 1, by differences in the fin formula-viz. D. 8 .14 and A. 3 .12 in place'of D. 3 . 12 and A. 2 .10 ; 2, by the scales of the ventral keel being ten in number instead of eight; 3, by the height of the body, compared with the length from the snout to the base of the caudal fin, being as 1 to 21, not as 1 to 2 ; 4, by the smallness of the suprascapulary spine. Again, from T. elongatus, Giinther (Cat. Fishes Brit. Mus. i. 10), it is abundantly distinct: e. g., 1. In that species the formula of the dorsal fin is 4 .11, and of the anal fin 3.9. 2. In the species now described the dorsal fin is much longer than high, whereas in T. elongatus its height equals its length. 3. The spines of that fin become shorter backwards; in the case of T. elongatus, longer. 4. The ventral fins are much shorter than the pectoral, whereas in T. elongatus these fins are of equal length. 5. The anal fin commences under the middle of the soft portion of the dorsal fin, whereas in T. elongatus it begins under the end of that fin. 6. The spine at the upper angle of the opercle is large, but in the case of the Australian species it is scarcely visible. 7. The lateral line has 27 in place of 65 scales. The following are the dimensions of the individual upon which the species is founded :- inches. Total length (the mouth being closed) 19| Height in the pectoral region 6| Thickness in the same region 2\ Head (mouth closed) 5| Eye, diameter 1 \ Distance from eye to eye over the arched head .... 2 Upper jaw, length 3f Width of open mouth 3f * Snout, length of If Dorsal fin, distance from snout. 6f -, length 6 - , length of fourth spine I \ , length of third and fourth rays 2\ Pectoral fins, length 3| , width of base -fa , distance behind snout «... 5\ Ventral fins, length 2| , width of base \ , length of spine 2\ Vent, distance of its vertical from snout 10| Anal fin, length 2-fa , height 2\ Tail, lowest height If Caudal, length 3\ , expanse 5 Ventral keel, length 4f , width of middle plates I |