71 Part III. — Twenty-fourth Annual Report 



Genus Zeugopterus. 



Zeuyopterus punctatus (Bloch). Miiller's Topknot. PI. i. b., figs. 42 

 and 43. 



The earstones represented by the figures 42 and 43 are from two 

 fishes, one of them being 8£ inches and the other 5 J inches in length. 

 These earstones are small and somewhat oval in shape, but deeply notched 

 and truncate in front. One side, the inner one, is slightly convex and 

 is longitudinally grooved, but the reverse side is smooth. Those of the 

 larger fish are nearly 4mm. long by 2*5mm. in greatest width: those of 

 the other fish are 3mm. in length, and rather wider than the larger one. 



Genus Zepidorhomhus. 



Lepidorhombus Whiff (Walb.). Sail Fluke, Whiff, or Megrim. PI. i. B., 

 figs. 31 and 32; pi. ii. b., figs. 1-5; pl. v., figs, 1 and 2. 



The earstones of a megrim about 17 inches long are represented by 

 fig. 1, pl. ii. b., and fig. 2, pl. v., and they measure about 7mm. in length 

 by nearly 5mm. in greatest width. The length of these earstones is thus 

 about the one-sixtieth part of the entire length of the fish. 



In the megrim, as has been already stated, the earstone on the left side 

 differs somewhat in shape from the one on the right side, and this 

 difference is observable even in the earstones of the smaller fishes, but 

 perhaps not in very young specimens ; I find that in such specimens the 

 characteristics peculiar to the species or genus are usually obscure or 

 undeveloped. This will be more readily perceived by comparing the 

 photographs of the earstones of the larger megrim mentioned above with 

 those of the two smaller fishes represented by figs. 31 and 32, pl. i. B., 

 and which measure respectively 168mm. and 87mm. in length. Compare 

 also with the earstones represented by fig. 5, pl. ii. b., which are those of 

 a fish 11 inches in length. 



In the examination of large fishes or of those of moderate size the 

 difference in the shape of the earstones is readily noticed, one of them 

 being pear-shaped — that is, broadly truncated and somewhat emarginate 

 at the posterior end, with the lateral margins boldly rounded and 

 converging towards the narrow anterior extremity ; the lower edge is 

 tolerably even, but the other is scarcely so regular. The curve of the two 

 sides is slightly different, and this makes the anterior extremity appear 

 as if it were turned somewhat upward. Each earstone is also slightly 

 incurved on the outer aspects, the inner being correspondingly convex. 



The other earstone, like the last, is also widest posteriorly, but the 

 posterior end is obliquely truncated and deeply, and sometimes irregularly, 

 notched. The entire lower edge is boldly curved and tolerably even, 

 but the upper margin, though it has the posterior portion nearly straight 

 or slightly rounded, and more or less distinctly crenulated, is towards the 

 front eud interrupted by a considerable break in its continuity ; this 

 break appears to be more distinct in the earstones of larger fishes, and 

 the presence of this break causes the anterior extremity to terminate in a 

 tolerably sharp point. 



I have already given the size of the earstones of the largest fish 

 examined, and the sizes of a few of the others will be found in the 

 annexed Table. 



