of the Fishery Board for Scotland. 67 
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. 
Molwa molva (Linn.). The Ling. Pl. 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 224 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 104 inches long, and which measure fully 55mm. Figs. 
24 to 26 represent the earstones of smaller specimens of ling ranging from 
8 inches to 7 inches in extreme length. 
Genus Onos. 
Onos tricirratus (Briin.). The Three-Bearded Rockling. Pl. i. B., figs. 
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 
akLout 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 112 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 cimbrius (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‘Omm. and the greatest width 
25mm. These earstones are thus only about the one-fiftieth part of the 
