160 FISSURELLA. 



F. alba Cpr. Mazat. Cat., p. 218. — F. gemmata Mke. Zeitschr. f. 

 Mai. 1837, p. 186 (probably; see Maz. Cat., p. 218.) 



Generally encrusted with coralline, as the specimens figured are. 

 The white, ribbed shell, with a dark line around the internal callus, 

 reminds one of the Cape Verde Island group of F. alabastrites, F. 

 Humphrey i and F. glaucopsis. 



F. tenebrosa Sowerby, Jr. PL 60, fig. 69. 



Shell similar to F. nigrocincta but more rounded, with cloudy 

 black rays ; riblets scarcely elevated, subnodose. Margin of the 

 aperture scarcely crenulated. A more rounded shell, more loosely 

 ribbed and cloudily black-rayed than the preceding [jP. nigrocincta'], 

 only slightly crenulated at the margin of the aperture. (Sowb.) 



" California." 



F. tenebrosa Sows. Thes. Conch, iii, p. 192, f. 67. 



Evidently very closely allied to F. nigrocincta, probably falling 

 within the range of variation of that form. 



F. ostrina Reeve. PL 34, fig. 54. 



Shell ovate, slightly conical, rather compressed at the sides, radi- 

 ately ridged, ridges subrugose, irregular, obscurely nodulous ; orifice 

 oblong, narrow, sides excavated in the middle ; very dark purple, 

 pinkish toward the orifice, greenish within. (Reeve.) 



Panama. 



F. ostrina Rve. Conch. Icon. f. 106, 1850. 



F. nigrocincta Carpenter. PL 45, fig. 5, 6. 



Shell oval, broad, conical, elegantly painted with radiating black 

 lines ; sculptured with delicate radiating strise ; orifice subcentral, 

 obscurely trilobed ; inside white, margin delicately crenulated, 

 denticulations black ; callus white, encircled by a black line. 



Differs from the young of F. alba in its greater breadth, less com- 

 pressed form, finer stria? and crenulations ; from F. nigropunctata in 

 the black line around the callosity ; and from both in the form of 

 the hole, which is trilobed, not contracted in the middle. (Carpt.) 



Length '75, breadth -52, alt. *3 inch. 



Mazatlan. 



F. nigrocincta Carp. Mazat. Cat., p. 217. — Sowb. Thes., p. 191, f. 

 64, 65. 



