1873.] MR. R. B. WATSON ON MADEIRAN MOLLUSKS. 389 



Rissoa coriacea, Manzoni. (Plate XXXVI. fig. 27.) 



Hab. Santa Cruz, 10-15 fathoms; Machico, 10-15 fathoms; 

 Piedade (Canigal), 25-35 fathoms ; Ponta de S. LourenQo, 25-45 

 fathoms ; Funchal Bay, up to 50 fathoms. 



There are two pretty-well-marked varieties of this species, of which 

 the one is larger in all its proportions, but distinctly longer relatively 

 to breadth, with half a whorl more, thinner, more delicate, more con- 

 tracted in lower part of each whorl. The other variety, from which 

 Signor Manzoni's description and figure have been taken, is more 

 frequent ; it is a stumpier shell, with sometimes a tendency to a very 

 slight thickening and rounding-over of the outer lip. 



Mr. Gwyn Jeffreys suggests that this should perhaps be classed 

 under Fossarus. Signor Manzoni confesses the difficulty he felt as 

 to its true place. It is certain that It. tenuisculpta and this species 

 must go together, probably in the end to fall under a new genus, for 

 the satisfactory establishment of which data are still wanting. 



l^tL fif\, Rissoa tenuisculpta, Watson. (Plate XXXVI. fig. 28.) 



Shell cylindrically oblong, thin, glossy, transparent, colourless. 



Sculpture. Longitudinal lines of growth few, faint, hair-like. 

 Spiral scratchings about ^TrW mcn a P art > a att l e irregular and 

 unequal, slightly fretted but not at all cancellated, very superficial, 

 quite as distinct on the upper whorls as on the base. On embryonic 

 whorl they are replaced by another set of spirals, about yrrVu incn 

 apart and slightly deeper-seated (J. e. less on surface) and stronger. 

 The point of junction of these two series is very faintly marked early 

 in second whorl. 



Colour uniform yellowish white. 



Spire elongated, cylindrically conical, ending in a blunt round tip, 

 which is a little inverted. 



Whorls 5, probably 6 in fully adult shell, of very gradual and 

 regular increase, very well rounded. 



Suture little oblique, deep, but open. 



Mouth a very perfect oval, only a little intrenched upon and flat- 

 tened across the belly, and very slightly and bluntly pointed above ; 

 open. 



Outer lip thin but not sharp, a very little separated from the body, 

 with a slight tendency to form a sinus above, advancing and slightly 

 expanded towards its outer lower corner, but not really channelled on 

 the base. 



Inner lip sharp, a little advancing, so as to leave a very small um- 

 bilical chink, continued thinly across the belly, and projected a very 

 little out from the body, so as to join the outer lip. 



Sh. M. 5. 4. 3. 2. 1. 



L -074 -029 -029 "018 -012 -007 "006 



B -034 -023 -023 '03 022 -016 01 1 



Hab. Ponta de S. Louren^o, 25-45 fathoms ; Funchal Bay, up to 

 50 fathoms. 



Mr. Gwyn Jeffreys says that this is the same as one of the deep- 



