488 Part III. — Twentieth Animal Report 



and somewhat resemble those of the Cod in shape, except that they are 

 rather more elongated ; they do not show the same amount of crenula- 

 tion on the edges nor is the concave surface corrugated — at least not so 

 distinctly as in those of the Cod. 



In the so-called flat-fishes, i.e., Turbot, Plaice, Witch-soles, and others, 

 the ear-stones are usually fiat, moderately thin, and more or less rounded 

 in shape. The ear-stones of the Witch-sole, Pleuronerfes cynrxjlossus, 

 are nearly circular in outline, and have the surfaces slightly rugose ; 

 those of the Plaice, Pleuronectes plate>i^a, are broadly oblong, their inner 

 surface is slightly irregular, and one edge is more evenly rounded than 

 the other ; the ear-stones of a Plaice 24 inches long were 12 millimetres long 

 by 7 broad. 



There is sometimes a considerable diflerence in the proportional size of 

 the ear-stones of different fishes ; those, for example, of a Lumpsucker 15| 

 inches long measured about 1| by 1^ mm., they were nearly round, but 

 had a small tooth-like process at one end ; those of a Lemon Sole 12 inches 

 in length were sub-rhomboid in shape, and measured 3| by 2 mm., while 

 those of a Long Rough Dab 10 inches in length, which were sub-rotundate, 

 measured 6 by 4| mm. The ear-stones of the Hake appear to be com- 

 paratively large ; those of a specimen of moderate size, but the exact 

 length of which I am unable to give, measured 24 mm. in length by 

 9 mm. at the broadest part, in form they are broadly dagger-shaped, one 

 edge is nearly even and gently curved, but the opposite margin is almost 

 pectinate. A Cat-fish 27 inches in length had ear-stones broad at one 

 end and pointed at the other, and measured 4 mm. by about 2| )nm. at 

 the broad end. The ear-stones of some of the smaller fishes, such as the 

 Worm Pipe-fish, require the aid of a hand-lens to see them properly. 



The shells of the smaller species of Mollusca are sometimes fairly per- 

 fect, and when that is the case it is not difficult to distinguish the more 

 common forms, but molluscan shells, even if not smashed by the teeth of 

 the fish, soon become corroded by the gastric fluid, and should the 

 sculpture be, as it often is, a specific characteristic, their identification is 

 made difficult and frequently uncertain. 



The Crustacea are on the whole more easily determined than most of 

 the other groups ; the test of the smaller forms is usually moderately 

 tough and flexible, so that they frequently occur in the stomachs of fishes 

 more or less entire, and even when there are only fragments available the 

 genus, if not the species, to which the animal they are part of belongs, 

 may be made out. In many of the species of the Amphipoda, for 

 example, there are certain appendages so characteristic that it is possible 

 by an examination of these to iudentify with a fair amount of certainty the 

 species which they belong to ; and in proof of this, reference may be 

 made to the following from among other species. The first and second 

 gnathopods of Amj)liilochus manwJens are characteristic of that species ; 

 the second gnathopods oi Stenofhoe marina and Aletojm poIte.na7ia are also 

 well-marked appendages. By the structure of the seventh pereiopods, 

 together with the form of the third epimeral plates of the metasome, 

 several species of Ampelisra, such as A. brerirorni^, A.riiacrorephala, and 

 A. asdmiliii, may be satisfactorily determined. The males of the three 

 British species of Ghei roc rates, of Protomeileia fasriata, and others may be 

 distinguished by the form and armature of the second gnathopods, and I 

 have frequently detected the presence of DuJii'Ma porreda and falcata by 

 the second gnathopods alone. 



The most of the Annelida appear to be readily acted upon by the 

 gastric fluid, for if they are even for a comparatively short time in a 

 fish's stomach the only evidence we have of their presence is a quantity of 

 mucus mixed up with which are fascicles of bristles, and perhaps some of 



