MARSHALL : ADDITIONS TO " BRITISH CONCHOLOGY." 285 



Var. elata Jeffr. — This is simply a slender facsimile of the type, 

 from which it gradually merges. It is usually more sharply keeled, 

 and resembles some specimens of O. eonoiJea var. australis. Those 

 from Scilly are almost cylindrical, while others may easily be mistaken 

 for the next, O. turrita. It is generally smaller than the type, but a 

 specimen from Guernsey is a quarter of an inch in length. 



Jeffreys' figure is perfect, and Forbes and Hanley's (2) are good 

 ones of the type and var. elata. 



O. turrita Hani. — A most troublesome species, and bewildering 

 in its many forms, there being every gradation from conical to 

 cylindrical and slender to stout, and they have an affinity with many 

 of the preceding species. Not only is it the most variable of the 

 British Odostomice, but also the most difficult to determine ; I have at 

 least a dozen variations collected from Torbay alone. Nor is it easy 

 to assign to it any permanent or arbitrary character, as all the 

 described ones have their exceptions. It does not always have a 

 keeled periphery, as stated by Jeffreys ; the penultimate whorl 

 is not always as large as the last, and it is not always without an 

 umbilicus. It is but one-third the size of O. unidentata, which 

 it most nearly resembles, and has the last whorl narrowed instead 

 of expanded, and a small contracted mouth which does not 

 extend beyond the outline of the shell. The range in size is 

 also very great ; it sometimes attains a line and a half in length, 

 while some of the dwarf forms, which are equally numerous and 

 variable, do not exceed half a line. Jeffreys' type figure of five-six 

 whorls is more prevalent in the north, where it is dredged; those from 

 the southern coasts live under stones at low-water mark, and are 

 shorter and more conical, with more compressed and fewer whorls 

 (only four besides the nucleus), the last one being two-thirds the length 

 of the shell instead of one-half. Both forms, however, interchange 

 and are often found together. The immature stages of the next 

 species are very much like some of the forms of this one, especially 

 a small cylindrical variety, which is frequent in Torbay and occasionally 

 elsewhere. Monstrosities are numerous, the body-whorl, and the aper- 

 ture appearing unusually liable to distortion. O. turrita is a common 

 species, and occurs everywhere and at all depths on our coasts. I 

 have found it most abundant at Falmouth, under stones at low water; 

 these are of a pale bluish white. 



Jeffreys' figure of the type is perfect ; Forbes and Hanley's (as 

 O. unidentata var.) are not good ; Sowerby's is a good figure of a 

 common form, but not the typical one. 



Var. striolata Aid. — Guernsey and Herm; Scilly 40 f.; Land's 

 End; Borough Island and Torbay; Freshwater West; Lismore 10 f. 



