73 



Part III. — Twenty-fourth Annual Report 



The earstones of two other plaice, each about 456mm. long (not 

 represented among the photographs), measured fully 6 '5mm. in length by 

 about 5 -5mm. at their greatest width, and 9mm. by nearly 6mm., and 

 thus agreeing fairly well with the others in their proportion to the length 

 of the fishes they belonged to. 



On comparing the earstones of the smaller halibut with those of the 

 larger specimens of long rough dabs and plaice, a certain similarity may 

 be traced both in the general form of the otoliths and of their markings 

 as well as in the proportion of the length to the depth (or width). It 

 will be seen that they are all broadly oval in outline, their lower edge is 

 evenly rounded, and the widest part of the otolith is apparently at the 

 posterior end. The earstones of Pleuronectes flesus and Pleuronectes 

 limanda, and of one or two others, are also somewhat similar in form to 

 those referred to. There is, however, at least one notable exception in 

 the Genus Pleuronectes, P. cynoglossus, or the Witch Sole, to be referred 

 to presently, the earstones of which are nearly circular in outline instead 

 of being oval. 



Pleuronectes microcephalus, Don. The Lemon Dab. PI. i. B, figs. 

 19-25. 



The earstones of the lemon dab are comparatively small and are not 

 very distinctly characterised. Fig. 19 represents those of a fish 15 inches 

 long, and they only .measure a little over 4mm. by about 2*5mm. To 

 show how small these earstones are it is only necessary to mention that 

 those of a long rough dab scarcely as large as this species had ear- 

 stones nearly double their length, while the earstones of a plaice that was 

 at least 4 inches shorter were one and a half times as long. In the 

 annexed Table the sizes of several other lemon dabs are given whose 

 earstones are represented by photographs on the accompanying plates. 



Figure on the 

 Plate, (i. b.) 



Size of the Fish. 



Earstones. 



Length. 



Depth. 



20 

 21 

 22 

 23 

 24 

 25 



12 inches. 

 7| „ 

 6| „ 

 »i ,, 

 4| „ 

 3* „ 



3*5mm. 

 3 Omm. 

 2-8mm. 

 2*5mm. 

 20mm. 

 l*7mm. 



2 'Omm. 

 l'omra. 

 lomm. 

 1 Smm. 

 1-Omm. fully. 

 1 Omm. 



The earstones represented by fig. 20 have the upper and lower margins 

 nearly parallel, one end is obliquely truncated, but the other is pointed ; 

 in the smaller specimens both ends are rounded, and they are all pro- 

 portionally smaller than those of the plaice or the long rough dab. 



Pleuronectes flesus, Linn. The Flounder or Fluke. PI. i. b., fig. 18. 



The earstones represented by fig. 18 were obtained from a fish of 

 average size, but its exact length was not recorded, and they are the only 

 examples included among the photographs of the present series. They 

 have an outline somewhat resembling the earstones of the plaice, and 

 measure about 6"5mm. in length by fully 4 , 5mm. at the widest part. 



