TETRAGONURUS ATLANTICUS. 135 



opening it, the lower jaw presents a most remarkable appearance from the extraor- 

 dinary elevation of its sides, resembling enormously high gums,* and shutting into 

 or within the upper jaw, like the high-raised sides of a box, or the arched ends of a 

 trunk with a round top, within its lid. Each side in fact forms a thin but higli and 

 convex arch within the mouth ; highest in the middle, and from thence descending 

 gradually towards the corners of the mouth, but falling much more rapidly and 

 steeply forwards towards the front, which is deeply notched : the greatest height 

 of these internal gum-like sides or walls in their middle, rather exceeding half the 

 length of the jaw from its tip to the canthus of the mouth. Thus the lower jaw 

 resembles the hollow square stem of a ship or boat, with steep high sides. All 

 this vertical internal part or wall is smooth and shining : below, from the canthus 

 to the tip, there runs a narrow horizontal band of imperfect scales, rough like 

 shagreen ; and this is all that appears externally of the lower jaw when the 

 mouth is closed. The notch in front is very deep ; the walls or gums being here 

 cut down quite to the rough external band. The tip however of the jaw below it 

 is still broad and truncate, flat and smooth. The upper jaw exhibits none of this 

 peculiarity of structure. It is however retuse or slightly notched in front, and the 

 teeth, as in the lower, are divided into two sets or divisions, by a little gap in 

 front. 



The teeth in the upper jaw are in a single row, divided as above explained into 

 two sets of from forty to fifty on each side, in ail from eighty to a hundred. They 

 are minute, conic, close-set, or regular, and finely pectinate : the front ones more 

 produced, and sharp or conico-acuminate, and somewhat incurved ; the hinder 

 ones becoming gradually smaller. Their points project forth from a band of semi- 

 transparent skin, which sheaths their base, through which their roots or lower 

 parts are distinctly traceable : this resembles perfectly a true gum, only it is free, 

 and not adnate or cohering to the roots of the teeth. The same kind of gum is 

 found in the similarly finely pectinate-toothed Blennies. Hence the supposed 

 analogy with the dentition of the MugiUdcB is not real, but in appearance only. 



Chevron of the vomer in front of the palate feebly armed or furnished with a few 

 fine teeth : its line behind running backwards in the middle of the palate between 

 the palatines, raised, and finely sermlate, like the palatines themselves. 



The lower jaw is similarly furnished on the edges of the high-arched sides or 

 branches with a single row of from eighty to a hundred teeth, divided into two 

 sets of forty or fifty each, by a much deeper-cut-down notch or gap than in the 

 upper jaw. The teeth also themselves are generally larger, and even more regu- 

 larly and beautifully pectinate than in the upper. Also they are not conic, but 

 much compressed, like little narrow lancets, with the points slightly recurved : or 

 they may be described as nari'ow-oblong, parallel, and close-set, like the teeth of a 

 comb, with the points of each cut off obliquely, but so as to present a generally 

 even cutting edge, like that of a fine and long-toothed saw. Contrary to those of 

 the upper jaw, they are smallest and shortest in front, increasing rapidly in length 

 and size towards the middle or high part of the side, and scarcely again diminish- 

 ing till quite at the hinder end of the jaw. Their base, as in the upper jaw, is 

 covered by the same sort of gum or band of thin transparent skin, tightly em- 

 bracing but not adhering to their lower half or base ; which can be seen through it 

 as far down as to the edge of the high-raised wall or sides of the jaw, in which 

 their root is fixed. 



The teeth in both jaws are distinctly bony, white, and glassy ; and they are 

 fixed firmly in their places ; thus offering in no respect analogies of structure with 

 the MugilidcB. 



* Wliat may be called more properly the gimis will be presentlj' described. 



