of the Fishery Board for Scotland. 



07 



posteriorly towards the upper margin more than it does forward, and the 

 posterior end is therefore moderately narrow and is also bluntly rounded, 

 as shown by the photograph. The earstones are slightly concave 

 outwardly and considerably thickened towards the anterior end, especially 

 on the lower aspect. 



Genus Molua. 



Molua molva (Linn.). The Ling. PI. i. a., figs. 19-26. 



The earstones represented by fig. 19 were obtained from a medium- 

 sized ling, but the exact length of the fish was not stated. These 

 earstones have a general resemblance to those of the coal-fish and lythe. 

 The anterior end, however, is not angular but forms a bold curve, which 

 merges into the upper margin. This margin is only slightly arched in 

 the middle part, then slopes posteriorly to the sub-central and narrow 

 rounded distal extremity ; lower margin nearly straight except near the 

 posterior end, where it converges to meet the upper margin. The otoliths 

 are about 20mm. in length by about 8mm. in their greatest width. The 

 earstones of young ling apparently differ to some extent from those of 

 larger fish in their form and structure. Fig. 22 represents the earstones 

 of a fish 22^ inches long, and though the general contour is similar to the 

 larger otoliths, the upper margin is not regular. These earstones measure 

 only about 9mm. in length. Fig. 23 represents the earstones obtained 

 from a ling about 10k inches long, and which measure fully 5*5mm. Figs. 

 24 to 26 represent the earstones of smaller specimens of ling ranging from 

 8-| inches to 7 inches in extreme length. 



Genus Onos. 



Olios tricirratus (Briin.). The Three-Bearded Rockling. PI. i. b., rigs. 

 9-12; pl. iv., fig. 18. 



The three-bearded rocklings possess earstones that are narrow and 

 elongated ; the upper and lower margins are nearly parallel, and when 

 viewed from the side are seen to be slightly sigmoid in outline and some- 

 what twisted. Those represented by fig. 11 were obtained from a fish 15 

 inches long, and measure nearly 8mm. in length — equal to about the one 

 twenty-sixth part of the entire length of the fish — and they are about 4 

 times longer than broad. These earstones appear, however, to vary a 

 good deal in length, for those taken from another fish only a little shorter 

 than the one just referred to measured about 6" 2mm., but the width is 

 at out the same as that of the other. It was also observed that the 

 otoliths of small fishes did not possess the sigmoid outline that char- 

 acterises the adult examples. Two specimens llg inches and 8 inches 

 long respectively had earstones measuring 4"5mm. and 3'5mm — the last 

 wanted the sigmoid appearance already referred to (see figs. 10 and 9). 



Onos cimbrins (Linn.). The Four-Bearded Rockling. PI. i. b., figs. 13-17 : 

 pl. iv., fig. 10-11. 



This species possesses earstones quite distinct from those of the three- 

 bearded rockling ; their outltne is obscurely triangular, two sides being 

 nearly equal and shorter than the third side, and this difference is notice- 

 able in the earstones of even small examples. Those represented by fig. 

 13 were removed from the ear-chambers of one of the largest of the fishes 

 examined. This fish measured 260mm. (fully 10 inches), while the 

 extreme length of the earstones was only 5 'Ornm. and the greatest width 

 2v5mm. These earstones are thus only about the one-fiftieth part of the 



