FISSURELLA. 169 



The specimens before me are less rayed than Gould's. A small 

 ■variety is described by him, as more solid, more elevated and 

 rounded, externally cinereous, the ribs smaller and rounded, without 

 radiating stria? and without purple rays, but sometimes with dots 

 about the apex ; outline arched-conical, fissure elongated. Interior 

 very pale green, the internal callus sometimes surrounded with 

 violet ; margin crenated on a smaller scale. It is figured on pi. 60, 

 fig. 83. I do not know whether this small form really belongs to 

 verna or not. I have specimens before me from TenerifFe, Canaries. 



F. verna belongs to a group of species comprising F. glaucopsis, 

 humphreyi, alabastrites, conioides and obtusa. The form and size of 

 the fissure is remarkably diverse in the several species. 



F. afra Quoy & Gaimard. PI. 59, figs. 36, 37. 



Shell ovate-oblong, convex, buffish painted with brownish-violet 

 rays, white within ; longitudinal striae obsolete ; foramen oblong, 

 compressed. 



This species resembles the F. nimbosa of Lamarck, but is not the 

 same. The summit is more elevated, and the aperture is more car- 

 ried forward ; there is also a difference in appearance. For the 

 rest, it is ovate, conical, obtuse at summit ; the fissure is ovate, con- 

 tracted in the middle. It is very finely striated radiately, and 

 marked in the same way with radiating bands of a violaceous-brown 

 on a yellowish-white ground. The fissure is bounded with darker. 

 (Q. et G.) Length 9, breadth 7, alt. 5$ lines. 



St. Iago, Cape Verde Archipelago. 



F. afra (Fisswelle de Praya) Q. et G., Voyage de l'Astrolabe, 

 Zool., vol. 3, p. 336 ; atlas, t. 68, f. 5, 6. 1834. 



Compare F. verna Gould. 



F. glaucopsis Reeve. PL 38, fig. 67 ; pi. 60, figs. 91, 92. 



Shell depressed, the base oval, summit a little in front of the mid- 

 dle ; sculptured with about 21 principal radiating ribs, and the 

 same number of smaller ones between them. Fissure small, oval. 



The form is much more depressed than F. alabastrites, being more 

 like F. verna. The color is pure white, with an eroded bluish tract 

 just around the perforation. Inside white (or the most delicate tint 

 of green), stained with black or purplish-black around the hole, 

 which is encircled by a black line. Margin coarsely toothed. 



Length 28, breadth 22, alt. 8 mill. 



Cape de Verde Is. 



