76 Part I1].—Twenty-fourth Annual Report 
Fam. SALMONIDA. 
Genus Salmo. 
Salmo salar, Linn. The Salmon. PI. ii. B,, fig. 31; pl. v., fig. 9. 
The earstone represented by fig. 31., pl. ii. B., measures about 7mm. in 
length and about 3°6mm. in depth. The length of the fish they were 
obtained from has not been recorded; I may mention, however, that those 
represented by fig. 9 on pl. v. are from a salmon weighing about 10 lbs., 
but, as in the previous example, the length of this fish was not stated. 
The earstones are of an oval form, with both ends moderately narrow and 
bluntly pointed, but one end is more drawn out than the other, as shown 
in fig. 9. 
Salmo (2) fario, Linn. The Brown Trout. PI. ii. B., fig. 30. 
The earstones represented on pl. ii. B. are from a trout weighing three 
quarters of a pound, which was caught in Loch Thom, near Greenock, 
many years ago. 
Genus Coregonus. 
Coregonus lavaretus, Penn. The Powan (or Pollan). Pl. ii. B., figs. 
20-27; pl. v., fig. 29. 
The earstones represented on pl. ii. B. are from Loch Lomond powans 
measuring 8 inches, 8 inches, and 74 inches in length. Those from the 
first two fishes are nearly of the same size—viz., about 5-5mm. long by 
3mm. in greatest width, one of the ends—(?) the anterior—is moderately 
* broad and has a rounded margin, but the other end is pointed; the lower 
margin is tolerably even, while the upper, which anteriorly is nearly 
parallei with the lower, slopes from about the middle to the pointed 
extremity at the posterior end. The earstones of the smaller fish measure 
about 5mm. in length and 25mm. in depth, and these have the posterior 
end rather more pointed than in the others. 
Genus Argentina. 
Argentina sphyrena, Linn. The Hebridean Smelt. Pl. i. B., figs. 44 
and 45; pl. iv., fig. 9. 
The Hebridean smelt is one of a small number of fishes that possess 
earstones of a shape so unlike those of other fishes that there can be little 
difficulty in determining the species the fish belongs to by the earstones 
alone. The earstones of two specimens are represented by the photo- 
graphs—figs. 44 and 45, pl.i.B. Fig. 9, pl. iv., gives a greatly enlarged 
representation of those in fig. 44. The fishes from which these ear- 
stones were obtained measured 83 inches and 8 inches respectively, while 
the earstones themselves measured about 3°5mm. in extreme length and 
depth—the length and depth being about equal. These earstones, which 
differ in form from those of the other fishes mentioned in this paper, may 
be described as broadly scaphoid or boat-shaped, the short lower margin 
representing the keel, and the longer upper margin with its two small 
prominences being the deck, while the obliquely truncated anterior end 
represents the bow, and the other and nearly rectangular end the stern. 
The extreme length of these earstones is rather more than the one-sixtieth 
part of the length of the fish. 
