MARSHALL: ADDITIONS TO "BRITISH CONCHOLOGY." 229 



Var. crassa Thomps. — Channel and Scilly Islands; Skegness; 

 Clyde. 



Var. angusta Jeffr. — Many places from Jersey to Shetland, not 

 uncommon. Every gradation between this and the type is to be found. 

 It is the prevalent form at Jersey, while a still more slender and 

 smaller form, with compressed whorls and shallower suture, occurs at 

 Guernsey and Scilly. I have the cylindrical monstrosity from Oban, 

 and the turreted one from the Clyde. 



O. pallida is almost as -variable as O. rissoides, and some specimens 

 will be found to run unpleasantly close to it; but it has a closer 

 affinity to O. albella, especially through the var. angusta. There are 

 two principal forms, a short-spired and a long-spired one; Jeffreys has 

 figured the latter and made it his type, while Forbes and Hanley have 

 adopted the short-spired form, although the latter is greatly in the 

 minority. Specimens of Jeffreys' dimensions I have seen from Guern- 

 sey only; the usual size is a line and a half, but the majority are 

 smaller. An elongated form has compressed whorls and an angular 

 mouth, another has rounded whorls, while a variety from the Clyde is 

 egg-shaped, with a very short spire and ample body-whorl, not unlike 

 Melampus bidentatus. Throughout the different forms, the shallow 

 suture and elongated mouth are pretty constant characters, and the 

 shell is never so thin as O. albella or O. rissoides, the only British 

 species likely to be confused with it. Jeffreys says the spiral striae 

 "may be detected with a lens of ordinary power," but only about twenty 

 per cent, are so, even in the strongest light. Clark was more than 

 usually mistaken in combining O. rissoides and O. albella with this as 

 dwarf littoral varieties. Neither of the former are dwarfs, and on a 

 fair comparison O. pallida cannot claim any preference in point of size. 

 Perhaps this was as near as he could ascertain from his limited methods 

 of observation, but more regard to their conchological characters 

 would have shown him that these species differ in texture, sculpture, &c. 



Forbes and Hanley's figures (as O. eulimoides) are fairly good of the 

 short-spired form ; Jeffreys' is better, but the base should be more 

 pointed and there should be no umbilicus. Sowerby's type figure (12) 

 is not good, having a round and projecting mouth, but his figure 13 

 (back view) is a good profile of the var. angusta. The figure of 

 O. crassa in " British Mollusca " is a carinated monstrosity, and not 

 Thompson's O. crassa, whose original figures in the Annals, 1 though 

 not very good, give a fair idea of the shell. 



Forbes and Hanley 2 adopted the name eulimoides for " what is 

 usually marked in cabinets as the pallidas of Montagu, with whose 



1 Ann. and Mag. Nat. Hist. ser. i, vol. 15, p. 315, pi. xix., f. 5, 1845. 



2 Brit. Moll., vol. 3, p. 273. 



