i8o 



THE BRITISH NATURALIST. [September 



with spots or bands in their normal form (though albinos occur in 

 most species), have a sharp outer tip without a trace of thickening in 

 the most fully adult state. The whorls form a very regular little 

 cone, being flattened and without much suture ; the sculpture, too, is 

 very slight, and does not at all affect the contour of the shell. Of 

 this group we have two members in British waters, R. cingilius, Mont, 

 (the type of the sub-genus) and R. semistriata Mont., both common and 

 littoral in their habitat. For the name R. cingilius, Canon Norman 

 and others have recently substituted the undoubtedly prior one of 

 R. tvifasciata, Adams, but it seems almost a pity to oust such an old 

 friend as cingilius. The older name certainly is apt in giving one a 

 clue to the species, as it emphasizes the distinguishing feature of this 

 Rissoa, viz. : the three reddish or brown bands on the last whorl, two 

 of them broad and very well defined, the third a shorter one at the 

 base. The rest of the shell usually has a varying yellow tint, while 

 at Weymouth, especially round the Hothe, orange-coloured shells 

 predominate with vanishing bands. Albinos of this species occur 

 sparingly with the type and are known as var. rupestris, Forbes. R. 

 cingilius is not smooth, but has numerous striae, distinct on the last 

 whorl, but almost absent above ; they are spiral, i.e., running with 

 the coil of the shell and are crossed by still finer lines longitudinally. 

 The length varies slightly up to about 3 mm. The species is 

 gregarious and to be found on almost any stony shore, under stones 

 deeplv buried in the shingle, from about half-tide downwards. No 

 criterion vv^ill be necessary beyond that of the two clear reddish bands; 

 the third one is not so evident. A pale but not pure-white variety is 

 var. gmphica, Turtori. I am not aware of any other named variety. 



R. Semistriata, Mont., is not such an easy species to identify as 

 the preceding, but 1 think that as before the easiest feature to rely 

 upon is the colouration. This takes the form of more or less oblong 

 blotches of red at set intervals along the upper margin of each whorl, 

 and a corresponding row of smaller and narrower marks, more streaky 

 along the lower margin. Between these two rows there is a well 

 defined plam area the ground colour being yellowish- white, the 

 markings, as usual, gradually die out towards the apex. The shell 

 is more solid, smooth and glossy than the last species, with a spire 

 less produced ; to the naked eye it usually appears to have no 

 sculpture at all ; the suture is very slight and the whorls much flat- 

 tened. It should be looked for alive at low tide under stones (but not 

 those deeply l)uried, as with. R. cingilius), but occurs much more 

 commonly m shell sand and is generally common in dredged materials. 

 The albino form of the species is called var. pum Jefl"reys, and occurs 

 with the type. Average length 2^^- mm. ^B. Toimlin, Llandaff. 



