282 Transactions. — Zoology. 



There are thus three species and a doubtful fourth with uufringed 

 spiracles : from these the Purakanui specimen differs in the following 

 characters : — 



(1.) From T. hebetans: 



a. In the position of the first dorsal fin ; 



b. In the presence of well marked emarginations separating the 



pectoral fins from the head ; 



c. In colour. 

 (2.) From T. narce : 



a. In the comparative size of the first and second dorsal fins ; 



b. In the absence of a well-marked longitudinal pit at the angle of 



the mouth ; 



c. In colour. 



(3.) From T. emarginata : 



a. In the position of the first dorsal fin ; 



b. In the anterior boundary of the head being curved instead of 



straight ; 



c. In the breadth of the disc being greater than the length ; 



d. In the tail being shorter than the disc ; 



e. In the absence of tubercles on the dorsal surface. 

 (4.) From T.fairchildi: 



a. In the position of the first dorsal fin ; 



b. In the relative size of the two dorsals ; 



c. In the more rounded form of the disc ; 



d. In the distance between the emarginations being fully six times 



the distance between the eyes, instead of the two distances 



being about equal. 

 According to Giinther, the most important of these characters are those 

 relating to the dorsal fins, namely, the position of the first dorsal with 

 regard to the pelvic fins, :;: and the relative size of the two dorsals. For 

 instance, in T. hebetans, " the first dorsal fin is twice as large as the second, 

 and situated nearly entirely behind the root of the ventrals," while, in 

 T. narce, " the first dorsal fin is not twice as large as the second, and only 

 its anterior half is opposite to the base of the ventrals."! 



* Dr. Giinther would earn the gratitude of morphologists if he would give the weight 

 of his authority to a much-needed change in the nomenclature of fins. Every one knows 

 that the fins of fishes are divisible into median and paired ; the former being either dorsal, 

 ventral, or caudal ; the latter pectoral or pelvic. If, then, the name " anal " could be 

 abolished, the so-called anal fins being called ventrals, and the so-called ventrals pelvics, 

 a very great improvement would be effected: the authority of such a book as the 

 " Catalogue of Fishes" could not fail to effect the change of names within a reasonable 

 period. 



t Giinther, I.e. 



