124 Mr. W. Thompson’s Catalogue of the Land and 
6. Planorbis umbilicatus, Mull. Jeffreys, Linn. Trans. v. 16. p. 384. 
P. marginatus, Drap. p. 45. pl. 2. f. 11, 12, 15; Gray, Man. p. 
265. pl. 8. f. 87, 88, 90; Turt. Man. f. 87. 
This species prevails in every quarter of the island, but is not ge- 
nerally distributed. Attached to stones at Ram’s Island, Lough 
Neagh, I find a small variety}+, about half the ordinary size, and 
which is concave beneath, with the keel obscure—Mr. Alder re- 
marked on some of these which I had the pleasure of adding to his 
collection in 1835—‘‘ Turton’s P. rhombeus, of which he sent me 
specimens, is the same thing in a younger state.” Mr. Jeffreys, in 
a letter dated Oct. 2, 1838, when acknowledging the receipt of the 
Lough Neagh shell, observed that he considered it distinct from P. 
marginatus, and that from a similar shell previously found at Cardiff, 
he had named the form P. inequalis. It is to a distorted individual 
of the P. marginatus, found in a pond at the College Botanic Garden, 
Dublin, that Capt. Brown applied the name of Helix cochlea (Irish 
Test. p. 528. pl. 24. f. 10.), and Turton that of Helix terebra (Conch. 
Dict. p. 62. f. 55.) —Mr. O’Kelly, to whom the shell belongs, always 
considered it P. marginatus, and as such noticed it in the Dublin 
edition of Pennant’s Brit. Zool., p. 363. The Rev. T. Hincks writes 
me from Cork that ‘‘ the var. of Plan. marginatus with the volutions 
elevated into a spiral cone was once taken in Ballypheane bog.” I 
have myself met with monstrous forms of several of the native spe- 
cies of Planorbis. 
7. Planorbis vortex, Mull. Gray, Man. p. 267. pl. 8. f. 91; Turt. 
Man. p. 109. f. 91; Drap. p. 44. pl. 2. f. 4, 5. 
Helix vortex, Mont. p. 454. t. 25. f. 3. 
S. Planorbis spirorbis, Mull. Gray, Man. p. 268. pl. 8. f. 98; Turt. 
Man. p. 115. f. 98. 
P. vortex, 6. Drap. p. 45. pl. 2. f. 6, 7. 
Helix spirorbis, Mont. p. 455. t. 25. f. 2. 
The species which my correspondents (chiefly judging from the 
descriptions and figures in Turton’s Manual) have considered as the 
P. vortex and P. spirorbis, are noted as generally common in Ireland 
—these shells merge so into each other that I was in the habit of 
putting all that were collected throughout the north together. On 
comparing these with examples of ‘‘ P. spirorbis” from the neigh- 
bourhood of Newcastle, and of ‘‘ P. vortex’ from that of London, 
presented me by Mr. Alder, I find that although some of them are 
as large as the P. vorter, have seven volutions, and a carinated 
edge to the lower one, that they are not of the extreme form desig- 
nated by this name, and consequently come under P. spirorbis ; so 
likewise do a number of specimens from the neighbourhood of 
Portarlington sent me by the Rev. B. J. Clarke—those from the 
river Shannon, favoured me by the Rev. C. Mayne of Killaloe, may 
+ The size is, I conceive, attributable to the coldness of the water and 
scarcity of subaquatic plants. 
