1866.] MR. J. Y. JOHNSON ON TKACHICHTHYS 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 num- 

 ber 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 2|, 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 . 1 1, 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 com- 

 mences 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) L9| 



Height in the pectoral region 6§ 



Thickness in the same region 2i 



Head (mouth closed) 5g 



Eye, diameter 1 1 



Distance from eye to eye over the arched head .... 2 



Upper jaw, length 3-| 



Width of open mouth 3f 



Snout, length of 1^ 



Dorsal fin, distance from snout 6^ 



— , length G| 



— , length of fourth spine 1 1 



, length of third and fourth rays 2| 



Pectoral fins, length 3| 



, width of base T 9 7 



, 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 2A 



, height 2| 



Tail, lowest height 1-| 



Caudal, length 3& 



■, expanse 5 



Ventral keel, length 4| 



, width of middle plates 1 



