MARSHALL: ADDITIONS TO "BRITISH CONCHOLOGYV 129 



varicose rib on the penultimate whorl, which distorts the last whorl 

 and the aperture out of its normal axis, similar to R. striata var. 

 distorta; they are two lines in length. A very thin and smooth 

 variety, with convex whorls, and having no colouring nor labial rib, 

 occurs in some rock-pools at Torbay, Saltcoats, Scarborough, and 

 Lerwick, narrow specimens of which are like a large var. exilis. 

 Another remarkable one is as broad as long, with a very short spire. 

 And there is an oval form, with a shallow suture, which is not 

 uncommon. The interstitial stria? varies in degree, but are often observ- 

 able with an ordinary lens. 



Var. semiCOStata Mont. — In this variety the longitudinal ribs 

 are evanescent or absent from the last whorl as well as from the three 

 upper ones. Captain Brown 1 appears to have described it under a 

 misapprehension ; his description and figures are those of the type, 

 while his alleged figures of the type (f. 55, 56) are impossible. In the 

 latter the longitudinal ribs usually end abruptly a little below the peri- 

 phery, being cut off by one or more faint spiral lines, but none of the 

 many forms of R. parva have the ribs prolonged to the base, as 

 figured by him for the type. 



Var. exilis Jeffr.— Scilly (Burkill and J.T.M.) : Falmouth; 

 Borough Island ; Torbay; Killala Bay ; Dornoch Frith. This variety 

 is rare. The whorls are convex, and it differs in that respect from 

 a dwarf of the var. interrupta, which is still smaller. 



The monstrosities are numerous. Among the most remarkable are 

 some from Scilly of a cylindrical shape, like a Cerithium, with others 

 of the var. interrupta, shaped like young Odostomia scillce; others have 

 a very extended aperture ; and one is a beautiful scalariform example 

 of the var. interrupta. My monstrosities of this species number 

 several hundreds, some of which are very curious. 



R. inconspicua var. ventrosa Jeffr. — Torbay; Loch Boisdale 

 and other parts of the Hebrides. Umbilicus more conspicuous. 



Var. variegata v. Mohr. — In weeds at low water. Most abun- 

 dant at Torbay and Cumbrae. The apex in this variety is less acute, 

 and the shell varies in shape from conical to oblong. 



Of R. inconspicua there are three principal forms : — (1), the typical 

 one, having longitudinal ribs and fine cross striae, figured well by 

 Jeffreys; this is mostly found on the south coasts; (2), finely can- 

 cellated with uniform longitudinal and spiral striae, most frequent in 

 the Hebrides ; and (3), smooth, thin, coloured with short streaks of 

 reddish-brown, spire more slender, aperture wider, and having no 

 labial rib, but sometimes one or two of the top whorls are finely 



1 Recent Conch., p. n, pi. 9, f. 1, 2. 



