CYLICHNA. 515 



being often a little elevated, the space behind it seems then 

 a little indented. The length of individuals is usually the 

 tenth of an inch ; their breadth is only half a line. 



This species has been taken at Exmouth (Jeffreys) ; and 

 Lamlash Bay, Arran, Skye, Zetland, and at Birterbuy 

 Bay, Galway (Barlee). It ranges to the Mediterranean. 



C. NiTiDULA, Loven. 



Minute, subcylindrical, without the least trace of spiral stri- 

 ulfe ; crown attenuated and rounded, without external volu- 

 tions, imperforated, or very nearly so ; aperture not perpen- 

 dicularly raised above, but bending over the crown. 



Plate CXIV. c. fig. 6. 



Bulla umUlicata, Mont. Test. Brit. vol. i. pi. 7, f. 4 (not description), copied in 

 Wood, Index Testae, pi. 18, f, 58, and Brown, Illust. 

 Conch. G. B. pi. 19, f. 9 (as Volvaria). 



Cylichna nitidula, Loven, Index Moll. Scandinav. p. 10. 



Bulla {Cylichna) umUlicuta, A. Adams, Thesaur. Conch, vol. ii. p. 592, in part, 

 pi. 125, f. 140. 



Two most closely allied shells have apparently been com- 

 prehended by Montagu under the name umhilicata. In 

 his description of the one for which we have reserved the 

 name, he does not cite his own delineation of the elongated 

 and scarcely perforated form that has been separated from 

 the more j^M^^^-shaped and umbilicated one ; hence it is 

 not improbable that after having described a somewhat 

 worn shell, he figured a better specimen of what seemed to 

 him the same species. 



The peculiar feature by which this species may at once 

 be discriminated from the three next shells, is the perfect 

 absence of all spiral striulre ; not a vestige of them can be 

 discerned even beneath the microscope. The shell is of a 

 pure and shining porcelain white, smooth or merely wrinkled 



