SCALARIA. 



thickened all round and reflected, most distinctly so in 

 those species whose volutions do not touch each other; 

 the lower part on the side of the Columella is formed in a 

 very indistinct manner into a sort of canal; this is more 

 observahle in some species than in others, but it may be 

 traced in all that we are acquainted with. A thin, horny, 

 spiral operculum closes the aperture. 



The principal species of this Genus is the shell that 

 has been so long and deservedly famous on account of its 

 elegance and rarity, namely, the Wentletrap, or Staircase 

 Shell, fine specimens of which in former years have 

 obtained enormous prices ; of late they have, however, 

 become more common, though the specimens now brought 

 to England are in no respect inferior to those which for- 

 merly produced such very high prices; indeed, most of 

 the species of this Genus are extremely elegant and 

 singular, not only the recent, but likewise the fossil 

 species which occur in most of the strata above the chalk : 

 several are engraved in " Sowerby's Mineral Conchology," 

 from the Crag and London Clay; Lamarck has published 

 others in the "Annales du Museum,'' vol. 4, from the 

 Calcaire grossiere of Grignon; they occur also in the 

 newer formations of Italy, perhaps contemporaneous 

 with our Crag, and these are published in ^'Brocchi's 

 Fossilia subappennina:" they occur also, but more rarely, 

 in the green sand. 



Of the recent species, which are marine, Lamarck 

 has described seven; by the addition of species already 

 known this number might be doubled — and together with 

 the fossil species their number will amount to at least 

 thirty. We have represented 



Pig. 1. Scalaria pretiosa. Lam. 



2. Clathrus. Turbo ClathruSy Linn, et auctm. 



3. raricosttty Lam. 



4. australis^ Lam. 



5. foliacea. This is an hitherto undescribed fossil species found 



in our Crag, by the Rev. G. R. Leathes ; we have named and characterized it as 

 follows : 



Sc. foliacea^ testa turrita, anfractibus disjunctis ; costis paulum distantibus, 

 tenuibus, latis, foliaceis, reflexis. — From nei;r Woodhall, iu Suffolk. 



