Characteristics of the Togue. 239 



are almost similar in the three, and broadly distinctive as 

 compared with the brook trout, and the sea and salmon trouts, 

 whilst the outline of the gill cover, and the relative dimensions 

 of the operculum (0), and its points of junction with the 

 sub-operculum (J>) in all the American lake trouts, assimilate 

 closely to the salmon (S. sa/ar), whilst the crescentic outline 

 of the pre-operculum (s) is broadly distinctive, and resembles 

 that of 5. ferox of Europe. 



In the New World lake trouts, the pre-operculum bulges to 

 a degree, owing to the enormous development of the great mas- 

 ticating muscle in front. The general features of the opercular 

 apparatus in lake trouts, as compared with other salmon oids, 

 are distinctive : the operculum (0) is four-sided, well rounded* 

 and of greater height than breadth ; the sub-operculum 

 (p) is nearly one-third smaller than the las(> and is triangular 

 in its upper half, elliptical in its lower borders, and terminates 

 at its articulation somewhat in the form of a fish-hook. The 

 operculum (s), with the exception of the siscowet, is long, 

 slender, crescentic, and almost vertical, with a prominent ridge, 

 and the usual foramina upon its anterior surface. 



The teeth of the togue are strong, slightly curved, and 

 conical ; those on the outer and lower maxillaries are the 

 largest. The vomer is armed with a few teeth in a cluster 

 or in regular double row, as is said to be the case in the 

 namaycush — although in the young of the former the teeth 

 run in a zigzag way down the bone in a single row for some 

 distance ; but in old fish there are usually seven. Two adult 

 male togues examined by me gave the following formula, 

 which it may be remarked is absolutely identical with that 

 given by Richardson as the scheme of dentition in the namay- 

 cush, viz., intermaxillaries, 7-7; labials, 19-19; palatines, 

 13-13 ; lower jaw, 19-19; tongue, 8-8; vomer, 7-7* 



It is worthy of note that in young and adolescent indi- 

 viduals of the togue, a third row of teeth is frequently observed 

 * " Fauna Boreali Americana," p. 182. 



