70 



Part III. — Twenty -fourth Annual Report 



gularly convex. One end is subtruncate, but the other is broadly rounded. 

 The earstones of a considerable number of long rough dabs have been 

 examined, and it has been noticed that though the larger examples 

 retained their characteristic shape there was some variation in the propor- 

 tion of their sizes to the length of fishes they belonged to. The two 

 largest of the fishes among the number selected for this paper measured 

 respectively 370mm. and 317mm. in length, their earstones — represented 

 by figs. 7 and 8 — are almost identical in size, and measured about 7'5mm. 

 and 5mm. in length and width. It has been observed that the length 

 of the earstones of most of the Pleuronectids examined are shorter in pro- 

 portion to the length of the fish than those of the more typical Gadoids. 

 The earstones of the two fishes mentioned above averaged, roughly, about 

 the one forty-fifth or forty-sixth part of the average length of the fishes. 

 It has also been noticed that where there is an increase in the width of 

 the otoliths there is to some extent a corresponding decrease in the length. 



In the annexed Table the length of other five examples of long rough 

 dabs are given, with the lengths of their earstones: — 



Figure on the 

 Plate, (iii. a.) 



Length of the 

 Fish. 



Earstones. 



Length. 



Depth. 



9 



10 

 11 



12 

 13 



10 inches. 



s ;, 



7 



5 ,, 

 H n 



About 6'5ram. 



5 3mm. 

 ., 4 -8mm. 

 Fully 3 -0mm. 

 About 2 , 5mm. 



f One 4 '5mm. and 

 \ one 5 •Oram. 

 About 3'8ram. 

 ,, S'omm. 

 ,, 2'5uim. 

 2 -Oram. 



The earstones of the smaller fishes become more and more rotundate as 

 the length of the fishes decrease. 



Genus Bothus. 



Bothus maximus (Linn.). The Turbot. PI. i. b., fig. 33. 



The earstones represented by fig. 33 were from a turbot of about the 

 average size (about 20 inches in length). One of them, which is barely 

 6mm. over all, in its general outline is very like one of those of the large 

 halibut already referred to (fig. 1, pi. iii. a.), but much smaller, and it is 

 fully 4mm. in width ; the other earstone, which is nearly of the same 

 length as the first, but about 4"5mm. in depth (or width), has a somewhat 

 different form, and differs also in having the entire margin distinctly 

 crenulated. This difference between these two earstones may be only 

 accidental, but the otoliths of another fish to be presently described show 

 that such variation may be normal. Whether it be so in the present case, 

 however, can only be ascertained by the examination of several specimens 

 of different sizes, but not the very young, where variations of this kind 

 tend to disappear. 



The earstones of the brill, Bothus rhombus, are not represented among 

 the specimens photographed, but they appear to resemble those of the 

 turbot. 



