100 PHYSOSTOMI. 



in those of our trout. Thompson (1. c.) observes that the coats of other 

 species of Salmones than S.farw (of which only the Gillaroo is set down as a 

 variety) become muscular from the same cause. He alluded to having found it in 

 8. ferox. Sir J. Richardson observes : " We may here note the existence of a 

 strongly-marked and peculiar variety, called the Gillaroo trout of Galway. It 

 is remarkable for feeding on shell-fish, in consequence of which (it is supposed) 

 the coats of the stomach acquire a great degree of thickness, from which peculiarity 

 it is sometimes called the gizzard trout." * Sir H. Davy remarks that " the charr 

 of the lakes of Southern Austria feeding similarly (to the Gillaroo trout) have a 

 like thick stomach." It generally prefers a rocky bottom, and is said to breed in 

 lakes in their shallower pails, and not to ascend rivers for this purpose. But it 

 is found in the Shannon, Lough Corrib, Lough Mask, Lough Derg, Lough 

 Melvin, &c. The colours of this variety may be due to the character of the food 

 it indulges in, while in some localities its flavour is considered excellent, in 

 others quite the reverse. In Lough Melvin it is somewhat hog-backed, fine in 

 colour, and well flavoured : in Lough Derg, soft, colourless, and inferior. Its 

 stomachs are occasionally served up in Ireland as gizzards. Thompson obtained 

 from the stomach of one example, about 8 inches long, above 1000 shells of 

 Limneus pereger, Valvata obtusata, and a few Cyclas cornea. Stoddart observes: 

 this variety is found in a small tarn or loch, situated on a shoulder of Ben 

 More, in Sutherlandshire, about three miles from Innisnadamph, named Mulach 

 Corry. 



Variety g Swaledale trout. Plate CXV, fig. 1 . 



B. xi, D. 12-13 (/_v 4 o) | 0, P. 13-14, V. 9, A. 10-11 ( s ), L. 1. 125, Ccec. pyl. 35. 



This variety, which is comparatively rather broad, was given me by Mr. G. 

 Brooks, F.L.S., who informs me that it is found in Oxnop Beck, Swaledale, 

 Yorkshire. The example figured is a female 10 inches in length. There is a 

 considerable difference in the form and proportions of the sevei-al examples.. 

 Colours it is the most beautifully-tinted form that I have seen, being finely 

 studded with black dots placed in a light circle, and likewise with numerous blue 

 marks and red spots. Its. dorsal fin is finely spotted, but the white anterior edge, 

 so constant in most freshwater forms, is indistinct or absent. Scales fifteen 

 rows between the posterior edge of the base of the adipose dorsal in a line passing 

 downwards and forwards to the lateral-line. Stomach thickened and similar to the 

 variety termed Gillaroo, which form, Dr. Giinther observes, possesses forty-four 

 cceca, consequently if a variation in the number of such are diagnostic of distinct 

 species, this is a variety of the Gillaroo. Respecting its exact habitat, Mr. Brooks 

 observes that the upper part of the beck runs over millstone grit, but as it leaves the 

 moor it gets upon mountain limestone, and from this point, for a mile and a half, 

 to the point where it joins the Swale, it is composed of numerous small falls, with 

 intervening little dark pools in which the trout lie. The beck is overhung all 

 the way (on the limestone) by trees, mostly alder, silver birch and hazel, but with 

 a good sprinkling of elm, mountain ash, &c. The beck is closely overhung and is 

 in a narrow ravine. 



Variety h. Crassapuill trout. 



B. xi-xiii, D. 12-13 ( 9 3 -i*o) | 0, P. 14, V. 10, A. 11 (), L. 1. 125, L. t. 27/32. 



Six examples of this exceedingly interesting variety were sent me by Mr. 

 Harvie-Brown in June, 1882. They were taken in Sutherlandshire, at Loch 

 Crassapuil, where they are looked upon as land-locked sea-trout. Their fin rays 

 are similar to those of Sahno levenensis ; a transverse row of teeth is present across 

 the anterior portion of the vomer, and a double row along its body. The preopercle 

 has a distinct lower limb in some, indistinctin others, while the shape of the subopercle 



* Hunter's experiments with hard and soft food on gulls, showed thickening of the muscular 

 wall of the stomach occurred due to increased use. 



