rLAS.siFi(ATi<».\ UY (;ii.i,-((»vi:i:s. 49 



In figure :2 oi this c\it, representing the {^ill-cover of tiie true 

 Sjilnion, it will strike :inv casual ()l)scr\cr that the lunder 



:0^ 



H. 



\.>i 



inarjjiu of tlu- \\lioli' coveiiuu' forms nearly a scmicirele, wliile 

 that (»f \o. ;}, tlu" Bull Trout, approaehes more nearly to a 

 rcctun<;ular fij^ure. lu the forniei-, the /iir-npcrrn/iiiii, the fore- 

 {?ill-cover, a, ditiers from the sanu' part, similarly n)arke(l, in 

 No. ."5, it heiuf^ nuire rectilinear ; while tlu> njicrruluin, the f^ili- 

 cover proper, », of the former slopes hiudward and backward ; 

 the same portion, a, in No. .*5, euttiu}? in a liori/.ontal line upon 

 the joints of the .tu/>-t,/H'rrii/inii and hitcr-opcrruhini. 



And in all respects both differ entirely from the arranj^ement 

 of the same part.> in the head of the Silver Trout, exhibited in 

 the cut last preceding, page IH. 



The most striking consequence of these (btrerenees is, that 

 a straight bne, drawn baekward from the front teeth of the 

 upper jaw, the nu)uth bc-ing closed, to the longest posterior 

 projection of the gill-cover, will, in the three fish, nin at a 

 totally different angle to the horizontal line of the body ; and 

 will occupy an entirely diff'erent situation in respect to the 

 eye; such a line in the head of the Salmon {Salmo Salar), and 

 in the Silver Trout {Salmo iMcuxtris), passing close below the 



