Freshwater Mollusca of Ireland, 



123 



the Falls, near Belfast, and about the same time procured others in 

 the rejectamenta of the rivers Blackwater and Lagan, in the same 

 neighbourhood. In the demesne of Portavo, near Donaghadee, and 

 in the vicinity of Portaferry, localities in the county of Down, it has 

 likewise occurred to me. The animal is dark gray ; tentacula very 

 pale gray — dead shells are white. It was the P. Icevis which was 

 marked with doubt as " P. glaber ? Jeff." in Phil. Mag. 1834, p. 300. 



4. Planorbis imbricatus, Mull. Gray, Man. p. 261. pi. 8. f. 94; 



Turt. Man. p. 111. f. 94; Drap. p. 44. pi. 1. f. 49—51. 

 P. cristatus, Drap. p. 44. pi. 2. f. 1 — 3. 

 Helix nautileus, Mont. p. 464. t. 25. f. 5. 



This handsome and well-marked species is known to me as occurring 

 throughout Ireland, with the exception of the extreme south, where 

 however there is little doubt that it exists. It is very variable in 

 form — the varieties 1 and 2, and the " monstrosity with the volutions 

 detached, and raised above each other" (Turt. Man.), I have procured 

 on the same plant. The entire animal, together with the tentacula, 

 are of a pale gray colour. 



5. Planorbis carinatus, Mull. Gray, Man. p. 262. pi. 8. f. 89 ; 



Turt. Man. f. 89 ; Drap. p. 46. pi. 2. f. 13, 14, 16. 



Is much less common than P. marginatus, but found in all por- 

 tions of the island — in the earliest catalogues it was inserted as in- 

 digenous. In the neighbourhood of Portaferry, county Down, and 

 about the city of Dublin (a recorded locality), it has occurred to me. 

 I have seen specimens which were obtained near Portarlington by 

 the Rev. B. J. Clarke ; at a lake near Tyrrell's Pass, Westmeath, by 

 Mr. Ovens ; and at Lough Gounagh (county Longford) by Mr. R. 

 Callwell, of Dublin f. 



In 1833 Mr. W. H. Harvey favoured me with specimens labelled 

 "P. planat,us, Turt. Man.," from Portumna on Lough Derg, an ex- 

 pansion of the Shannon, where he stated that the form was frequent, 

 noting it at the same time to have been found by him at Ballitore 

 (county Kildare), where it is very rare — these shells correspond ex- 

 actly with Turton's description of P. planatus, Man. p. 110. This 

 seems to be the common form (though the normal one does likewise 

 occur) at Lough Derg, as testified by specimens since obtained from 

 Portumna and KillaloeJ, near its northern and southern extremities 

 — some from Nenagh (county Tipperary) have been kindly submitted 

 to my inspection by the Rev. T. Hincks of Cork ; near this city the 

 " P. planatus " is noticed by Mr. Humphreys as met with. Mr. Al- 

 der and Mr. Forbes consider the Lough Derg shell P. carinatus, 

 and, according to the former, it is the P. disciformis, Jeff. 



f Mr. Edw. Waller has favoured me with marl shells of tins species from 

 Finnoe, and remarks that it is the only shell found there in marl that is not 

 to be had in a living state; but this he attributes to the draining of a marsh. 



X To the kind attention of Mr. John J. Marshall of the former, and the 

 Rev. C. Mayne of the latter place, I am indebted for them. 



