18/3.] MR. R. B.WATSON ON MADEIRAN MOLLUSKS. 3/3 



(Journ. de Conch. 1868, pi. x. fig 1) has, on the whole, fairly 

 caught the general character of this shell. The really bad features 

 of the figure are : — the mouth, which fails to give the angulation 

 at the junction of the pillar and the tip at the extreme base ; the 

 lip, which is represented as bevelled from the interior of the mouth 

 outwards to the outside of the shell, whereas it is the inner margin 

 of the lip which projects as a flange ; and the spire, which is 

 made to form an almost perfect cone instead of rising strongly 

 in steps in consequence of the depth of the suture and the angular 

 droop of each whorl below the suture. 



I here subjoin Rissoa spreta as a mere variety of R. macandrewi. 

 I have long held it to be a different species ; and the two can be 

 unfailingly distinguished, there being no connecting links. The 

 general shape, the surface-sculpture, the form of the suture, of the 

 apex, and of the pillar present slight differences ; but the really 

 strong points of distinction are the fosse on the base, the rounded 

 swell of the whorls out of the suture, the more perfectly oval mouth 

 without angulation on the base, and the absence of the distinctively 

 white mouth and base. Beyond doubt it has a better claim to 

 specific recognition than very many received species ; and I am far 

 from convinced that it will not ultimately be accepted as a distinct 

 species. At the same time, after very careful study of a large 

 number of these specimens, I do not feel quite certain that it really 

 is a distinct species ; and where any doubt exists it ought to weigh on 

 the side of suppression, any thing being better than a multiplication 

 of false species. Mr. Gwyn Jeffreys, too, holds my R. spreta for a 

 mere variety of R. macandrewi ; and what is, with me, stronger than 

 all, I fail to find any difference in the embryonic whorls ; and identity 

 jn the earliest development must outweigh much later diversity. 



/ C.%x, Var - spreta, Watson. (Plate XXXIV. fig. 9.) 

 /ft) t Hab. Santa Cruz, 10-15 fathoms; Machico, 10-15 fathoms; 

 Piedade (Cauical), 10-15 fathoms; Ponta de S. Lourengo, 25-50 

 fathoms ; Porto Santo, up to 50 fathoms. 



This variety has some resemblance to R. crispa, but is not so 

 hunchv, its spiral threads are not so close, the spiral striolations are 

 not nearly so distinct, the spiral furrows and threads on the base are 

 not nearly so strong, the longitudinal ribs are more numerous, not 

 so sharp-topped, not so curved ; above all, these ribs do not cross the 

 suture to lap up on the previous whorl. The mouth lies more 

 straight in the line of the shell's length. 



#A Rissoa moniziana, Watson. (Plate XXXIV. fig. 10.) 



Shell conic-oval, thinnish, not glossy, frosted, transparent; whorls 

 rising in steps. 



Sculpture. Longitudinal ribs very rarely present on penultimate 

 whorl, indistinct, rather irregular, narrow ; somewhat oftener they 

 appear on body-whorl very indistinctly below the suture, and even 

 extend below the periphery, but generally, when seen at all, resemble 

 faint irregular puckerings close below the suture. Labial rib is 



fy 



