414 ME. F. DAY ON BEITISH SALMONES. 



were called G-illaroo trout by persons wlio distinguish, these from 

 the ordinary state of the fish, belieying them to be a distinct 

 species." Sir Humphry Davy remarked that if they are the 

 common trout which have gained the habit of feeding on shell- 

 fish, " they have altered in a succession of generations. The 

 common trout of this lake have stomachs like other trout, which 

 never, as far as my experience has gone, contain shell-fish ; but 

 of the Grillaroo trout I have caught with a fly some not longer than 

 my finger, which have had as perfect a hard stomach as the larger 

 ones, vrith the coats as thick in proportion and the same shells 

 within ; so that this animal is at least now a distincb species, and 

 is a sort of link between the trout and charr, which has a stomach 

 of the same kind with the Grillaroo, but not quite so thick, and 

 which feeds at the bottom in the same way." Sir J. Bichardson 

 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." 



I must confess being unable to understand by what process of 

 reasoning any ichthyologist who considers the common trout and 

 the great lake-trout distinct species can admit that, if both 

 Salmo fario and S. ferox have thickened walls to their stomach, 

 the first is to be constituted a distinct species as S. stomacliicus, 

 whereas in the latter it is merely to be deemed a variety. 



Salmo gillivensis, Griinther, 1865, or S. estiiarius, Knox (' Zoo- 

 logist,' 1855, xiii. p. 4662), is similarly coloured to freshwater 

 forms ; while the young (in the National collection) so exactly 

 resembles the S. cornuhiensis, that it is impossible to doubt their 

 specific identity. Knox's example had 60 vertebrse, similar to 

 the number present in the British-Museum specimen. 



The last British form which I propose briefly alluding to is 

 the Loch-Leven trout, Salmo levenensis, that appears, at least 

 from the specimens I have examined, to possess a considerably 

 shorter head than any of the varieties of the freshwater non- 

 migratory brook-trout ; while the number of its caeca has been 

 observed to vary from 49 to 90. This appears to be probably 

 a descendant from some marine form which, having obtained 



