MADEIRAN PERUSSACI/E. 267 



62. F. SCAPTOBIA Bourguignat. PL 45, fig. 28. 



Shell small, oblong, very fragile, diaphanous, polished, 

 smooth, pale corneous. Spire short, rather acute, the apex 

 obtuse. Whorls 6, hardly convex, the first regularly increas- 

 ing, the last two large, separated by a superficial duplicated 

 suture, the last half the total length or longer. Aperture long- 

 piriform acutely angular above. Columella straight, slightly 

 whitish, slightly twisted, subtruncate, and not reaching the 

 base of the aperture. Peristome acute, unexpanded, fragile, 

 the outer margin lightly arched forward, margins joined by a 

 very thin callus. Length 6.5, diam. 2.5, aperture 3 to 3.5 

 mm. (Bgt.}. 



Algeria: around Constantine, Philippeville, Bougie, etc.; a 

 rare species. 



F. scaptobia BGT., Amen. Make., i, p. 207, pi. 19, f. 4-6 

 (1856); Malac. Algerie, ii, p. 61, pi. 4, f. 23-25. PFR., 

 Monogr., iv, 622. KOBELT, Iconogr., vii, p. 32. 



Smaller than F. debilis, more delicate, more fragile and less 

 glossy; the spire is shorter, increase more regular; the aperture 

 is longer and narrower in its upper part. Known only by 

 Bourguignat' s account. 



Madeiran Ferussacise. 



With the exception of F. folliculus, probably introduced, the 

 Madeiran species of Ferussaria have probably diverged from a 

 single stock, or perhaps two allied stocks, which reached the 

 archipelago in early tertiary time. The forms with parietal and 

 supraparietal lamellae have probably retained more characters 

 of the old stock, while those with toothless apertures seem to 

 be secondarily simplified. The occurrence of lamellae on the 

 parietal wall in several otherwise diverse Madeiran branches 

 apparently points to this conclusion. Such lamellae, when 

 present, are homologous with those of continental tertiary and 

 recent species of Azeca, Pegea, Calaxis, etc., and can hardly be 

 of independent origin. 



Original sources of information on Madeiran Ferussacise. are 

 Lowe's several papers, cited below, Watson's descriptions of the 

 soft parts, and Wollaston's excellent resume in the Testacea 



