FERUSSACIA, MADEIRA. 277 



This species seems well distinguished from F. gracilis by the 

 constantly larger size, less fragile shell, and somewhat stronger 

 columellar fold as seen obliquely in the mouth. It is a smaller 

 species than F. producta, with less sinuous outer lip and wider 

 aperture. Figured from a specimen from the Lowe-Wollaston 

 collection. 



Var. mbtda (Lowe). PI. 39, figs. 17, 18, 19. 



Shell smaller, relatively narrower and more acute, the upper 

 part of the aperture narrower. Length 6, diam. 2, aperture 

 2.6 mm., or smaller, length 5 mm. Whorls 6-7. 



Ilheo de Cima and Ilheo de Baixo, and on the neighboring 

 Pico de Baixo on Porto Santo (Wollaston'). 



Achatina gracilis var. subtda LOWE, P. Z. S., 1854, p. 200. 

 Not Achatina subula Pfr., 1839. 



Figured from Lowe-Wollaston collection examples. The 

 name is preoccupied, but it is doubtful whether the form is 

 worth another. 



Var. ventricosa (Paiva). 



"Shell more ample, very glossy." Ilheo de Fora, at the end 

 of the Ponta de Sao Lourenco, Madeira, coll. by the Rev. R. 

 Boog Watson. 



Achatina gracilis var. ventricosa COSTELLA DE PAIVA, Mono- 

 graphia molluscorum terrestrium fluvia.lium lacustrium insu- 

 larium Maderensium, p. 108 (1867). 



An insufficiently defined form, placed by the Baron de Paiva 

 next to terebella, which he treats as a variety of gracilis. It may 

 be identical with the following. 



Var. laurentiana n. var. PI. 40, figs. 30, 31. 



The shell resembles terebella but is thinner, with a narrower 

 subsutural white band, less obliquely descending last whorl, 

 and a longer, much narrower aperture, which in its acuminate 

 posterior part and forwardly sloping lip resembles that of F. 

 producta. The columella is more distinctly truncate at base 

 than in terebella, and in oblique view in the mouth its weak 

 spiral fold is lower down. The outer lip is perfectly thin at the 

 edge, and in profile view it is more amply dilated forward. 

 Length 6, diam. 2.1, length aperture 3.25 mm.; whorls 6. 



