314 KEY. E. B. WATSON ON" THE 



307. Scalaria frondosa, 1829, J. Sow. Min. Conch, ti. 149, 

 dlssvii. 1 ; Searles Wood, Crag Moll. i. 92, viii. 15 ; 

 Tiberi (as 8. solufa), Jour, de Couch. 1863, p. 159, vi. 3, & 

 1868, p. 84, V. 2. — I got this species iu from 10 to 50 fms. 

 on the whole S.E. coast of Madeira, from Fuucbal to 

 Puuta de Sao Lourengo, and also from Porto Santo ; but 

 the specimens were few and were all young shells. It did 

 not occur in any other collection. 



iSJiell pure ivory-white, glossy, hunchy, that is very broad 

 in proportion to height, with well-rounded rather depressed 

 whorls, a bfoad very fine pointed spire, distant strongish 

 oblique ribs spiralled, without an umbilicus. Sculpture — 

 Longitudinals : each whorl is obliquely crossed by about 

 14 strongish but not thick, projecting reverted ribs, which 

 with a very marked sinistral twist run continuously from 

 whorl to whorl down the spire ; each rib runs out near the 

 suture into a well-marked but generally bluntish tooth ; 

 hesides the ribs the whole surface is finely scored, not 

 roughened, by striae, strong at the base of each rib. Spirals : 

 the whole polished surface of the shell, including, but 

 more faintly, the ribs themselves, is marked somewhat 

 feebly by flatly rounded spiral threads, which, somewhat 

 crowded on the earlier whorls, are on the later whorls parted 

 by interspaces about as broad as the threads. Colour 

 ivory-white, but a little translucent. Whorls probably 6 

 or 65, but of full-grown shells only fragments presented 

 themselves — the largest as measured below has 4|, exclu- 

 sive of those of the embryo. Suture somewhat oblique, 

 deeply impressed. Apex a very perfect small sharp cone 

 of 4 complete whorls which are barely convex, with a linear 

 suture : they are polished but microscopically cancellated 

 by longitudinal and spiral scratches. Mouth a very little 

 elliptical, rather small. Outer lip broadly expanded into a 

 thin lamina, which is continued all round, leaving a kind of 

 furrow, but no chink between it and the body-whorl. 

 li. 0-21. B. 0-11. 



I have described this species because the existing de- 

 scriptions are so vague that identification is extremely 

 difficult, as is proved by the ten synonyms quoted by 

 Jefi'reys, P. Z. S. 1884, p. 136. My own identification is 

 somewhat of a guess, but if wrong can be checked from 



