Freshwater Mollusca of Ireland. 125 
be placed under P. vorter, as may those also collected at Lough 
Gounagh, county Longford, by my friend R. Callwell, Esq. of Dublin. 
Is the more prominent keel, with other differences necessarily at- 
tendant on it, as form of mouth, &c., sufficient for specific distinction 
between P. vortex and P. spirorbis? Under Planorbis disciformis 
Mr. Alder has well remarked, that ‘the degree of carination is so 
very variable in different individuals of the same species, that it is 
rather fallacious as a distinguishing character.” Mag. Zool. and 
Bot. vol. ii. p. 118. 
Specimens of P. compressus, Michaud, from Lorraine, with which 
I have been favoured by their describer, are identical with those of 
P. vortex before noticed as from Mr. Alder. Examples of P. leuco- 
stoma, Michaud, with which I have been presented by this most li- 
beral author, differ only from Mr. Alder’s P. spirorbis in having a 
white rim within the mouth—on this subject see Supplement to 
Mr. Alder’s Paper in the Newcastle Transactions, and Mr. Gray’s 
edition of Turton’s Manual, p.267; in this work P. leucostoma, Mich., 
is referred to P. vortex, but if this is to be considered distinct from 
P. spirorbis, to the latter P. leucostoma must be referred. 
9. Planorbis nitidus, Mull. Gray, Man. p. 268. pl. 8. f. 93. 
P. fontanus, Turt. Man. p. 110. f. 93. 
P. complanatus, Drap. p. 47. pl. 2. f. 20—22. 
Helix fontana, Mont. p. 462. t. 6. f. 6. 
Although somewhat rare, this species is distributed over Ire- 
land. On some living specimens taken near Belfast in Dec. 1834, 
by Mrs. Hincks, and kindly sent to me, the following note was made 
—‘‘tentacula moderate, or rather short and uniform in colour with the 
body of the animal, which changes with age, the adult (with shell 
21 lines in diameter) being black; younger individuals pale gray— 
the shells of the latter are much the more transparent.”” These ani- 
mals seemed indifferent which side of the shell was uppermost, and 
when undisturbed often moved along with what is termed the under 
side next the surface of the water. 
10, Planorbis contortus, Mull. Gray, Man. p. 270. pl. 8. f.96; Turt. 
Man. p. 113. f. 96; Drap. p. 42. pl. 1. f. 39—41. 
Helix contorta, Mont. p. 457. t. 25. f. 6. 
Like the P. albus, generally distributed over Ireland, but of more 
frequent occurrence, and in greater quantity where found than that 
species. 
Sect. II. OpeRcULATA. 3 
Fam. CycLosTtoMID&. 
Gen. Cyciostoma, Lam. 
1. C. elegans, Lam. Gray, Man. p. 275. pl. 7. f. 75; Turt. Man. 
p. 93. f. 75; Drap. p. 32. pl. 1. f. 5—8. 
Turbo elegans, Mont. p. 342. t. 22. f. 7. 
Dr. J. L. Drummond informs me, that when at Sandymount near 
