78 



Part III. — Twenty-fourth Annual Report 



broadly rounded, and the posterior portion of the upper margin is also 

 crenulated. The sizes of the various specimens referred to and of their 

 earstones are given in the annexed Table : — 



Figure on the 

 Plate. 



Length of the 

 Fish. ; 



Earstones. 



Length. 



Depth. 



15 (PI. iii. B.) 



16 



17 



18 



19 



20 



21 



22 



23 



24 



314mm. 

 292mm. 

 279mm. 

 266mm. 

 235mm. 

 230mm. 

 215mm. 

 205mm. 

 156mm. 

 125mm. 



Not quite 4 '5mm.* 

 About 5 'Omni. 



,, 4 '5mm. 

 Nearly 5 '0mm'. 

 Fully' 5 -0mm. 



, 5'0mm. 

 3 •5mm. 

 About 3"5mm. 



,, 2"7mm. 



,, 2*0mm. 



Fully 2 0mm. 



2 '0mm. 



2 -0mm. 

 About 2 -0mm. 

 Nearly 2 -5mm. 



2 '5mm. 

 Scarcely 2'Omm. 

 Fully l-.lmm. 

 About 1 -5mm. 

 Fully 1 -Omra. 



The comparative sizes of the earstones of the herrings given here varied to 

 some extent, ranging from about the fiftieth to the sixtieth part of the 

 length of the fish they belonged to. 



Clupea sprattus, Linn. The Sprat. PI. iii. b., figs. 25-32; pi. v., 

 figs. 15-17. 



The earstones of the sprat are extremely small, and easily missed. 

 They resemble those of the herring to some extent, but are comparatively 

 shorter and broader, and even very small specimens exhibit this charac- 

 teristic difference. The earstones of the largest of the sprats examined 

 for this paper, and which measured about 3| inches in length, were only 

 about l a 5mm. in extreme length by 1mm. in depth. Other two sprats. 

 3 1 inches long, showed scarcely any difference in the size of their ear- 

 stones from that of the specimen just referred to {see figs. 27 and 28). 

 The position of these otoliths in the ear chamber is similar to that of the 

 herring — that is, the narrow part of the earstone is towards the front of 

 the head, and the upper margin is more irregular in outline than the 

 lower. The earstones represented by fig. 29 are from a fish 3-^ inches 

 (84mm.) long, and are about 1mm. in length by 0'7mm. in depth. The 

 otoliths represented by figs. 30 to 32 are from sprats measuring 72mm., 

 67mm., and 60mm. long. 



Clupea pilchardus, Bloch. The Pilchard. PI. iii. b., fig. 33 ; pi. v., 

 fig. 32. 



The earstones of the pilchard, as will be seen from the photograph, 

 are somewhat similar to those of the herring, both in form and size, 

 except that they are rather more pointed at the anterior end. The fish 

 from which these earstones was obtained was 6| inches (17 1mm.) in 

 length, and the earstones themselves measured 3mm. by about l*2mm. 



'The earstones of this specimen were imperfect. 



