REPORT ON THE GASTEROPODA. 37 



partition. Sculpture : Longitudinals — from the apex to the cleft across the middle of the 

 hack runs a broad raised keel, flat on the top, where it is scored by the minute, delicate, 

 sharp, prominent, close-set, but not contiguous scars of the old cleft ; on either side it is 

 bordered by a sharp marginal line : from these marginal lines branch off feeble irregular 

 diveroirjo- threadlets, between which, as they go wider apart, others arise ; the intervals 

 between them are two to three times the breadth of the threadlets. Spirals, strictly 

 speaking, there are none, but the whole surface is scored at right angles to the longitu- 

 dinals with a series of threadlets, very similar in form, but rather more closely set ; these 

 radiate from the apex and indicate the old mouth-edges. Colour porcellanous white, 

 which is dead on the threadlets, but almost translucent elsewhere from the extreme thin- 

 ness of the shell. Apex : At the posterior end of the shell there is a narrow, rounded, 

 prominent beak, within which, a little bent to the right and projecting slightly above the 

 margin of the mouth, is the minute apex of one whorl. Mouth oblong. Margin minutely 

 denticulated by the ends of the ribs ; cleft in front by a strong, parallel-sided, blunt-ended 

 fissure ; behind, it is peculiarly patulous, being markedly bent outwards from the line of 

 attachment of the septum, this bending being strongly shown on the outside of the shell. 

 Inside glossy, smooth ; a strong depression corresponding to the exterior keel extends 

 from end to end of the shell. Septum: A little way within the margin, and deepest at 

 the end, is the short oblique septum, which is faintly arched, with a concave edge in 

 front. L. 0-38 in. B. 0-2. H. 0-12. 



The present species, though somewhat chipped, is of great beauty. It differs from Zcidora 

 calceolina, A. Ad., which is rudely cancellated, and is also wider and more depressed. It is liker 

 Zcidora reticulata, A. Ad. ; but is larger and deeper, has the old cleft-scar raised on a projecting ridge 

 which forms a strong internal furrow, has the beak sharper and more projecting, the form is more 

 oblong and more pinched-in at the sides, the sculpture-lines are much finer and less regular than in 

 that species. 



Professor Seguenza has had the kindness to send me a careful sketch of the solitary specimen 

 which exists of his Crcpiemarginida reticidata from the Astian or Middle Pliocene of Rhegium in 

 Calabria (see Formazione Terz. di Reggio-Calabria, p. 273). It proves, as I inferred from the 

 description, to be a Zcidora ; and as in that genus reticidata is a specific name already used by A. 

 Adams, I would propose Zcidora scgucnzm for the Calabrian fossil. As compared with Zcidora 

 naufraga, this Calabrian fossil is much higher in front, much lower behind, where also it is much 

 broader and rounder, with a less pinched-in apex ; it is more widely ribbed, the scores on the scar 

 are wider apart and coarser ; internally the edge is more coarsely crimped, and the septum is very 

 much larger, being much more prolonged forward, and is horizontal instead of oblique ; the old cleft- 

 scar, too, is not raised on a projecting ridge, and does not form any internal furrow. 



I regret extremely to have no knowledge of Zcidora ligustica, Bellardi, beyond that of its name, 

 and the fact of its belonging to the Pliocene of North Italy. I wish, however, to call attention to 

 it, that some other person more favourably situated than myself may institute a comparison between 

 it and the " Challenger " species. 



