MAZATLAN UNIVALVES 173 



225. BULLA ? NEBULOSA, Gould. 



U. 8. Expl Exp. Moll.MJce. in Zeii. f. Hal 1850, p. 162, 



no. 2. 



A very few thin, subglobose shells were found, with a small 

 umbilicus, which are undistinguishable from the young of B. 

 nebulosa ; a species which, along with other points of simil- 

 arity, shews the spirally striate umbilicus, and traces (though 

 faint) of the rugosely striulate surface, of B. Adamsi. B. 

 nebulosa is quoted from Guaymas, and may be one of the very 

 few Californian species which cross the Gulf. I strongly sus- 

 pect however that these are but aberrant forms of the young 

 B. Adamsi ; which varies not a little in outline, solidity, and 

 size of umbilicus. The adult shells are sufficiently distinct. 

 Long. 1', lat. '7. 

 Hob. Sta. Barbara, Nuttall. San Diego, Lieut. Green. 



Guaymas ; in sand, 12 in.; Mus.Cuming. Mazatlan ; Menke. 



?Do. jun. extremely rare ; Lpool Col. 



Tablet 788 contains the most characteristic specimen. 



226. BULLA ? QUOYII, Gray. 



Sow. Thes. Conck. sp. 48, pi. 173, f. 71. 



A very few small specimens were found, differing from B. 

 Adamsi in the following points. Surface much more strongly 

 and closely striulate ; outline flattened towards the umbilicus, 

 at an angle of about 60. Umbilicus strongly striate, bounded 

 by a blunt angle. Long. '5, lat. *3. 

 Hob. Gallapagos, Cuming. ? Mazatlan ; extremely rare ; 



L'pool Col. 



Tablet 789 contains 3 minute sp., probably belonging to this 

 species. 790, the ? adult specimen. 



227. BULLA EXAEATA, n. s. 



B. t. parvd, ellipticd, compressd, aperturd elongatd, angustd ; 

 fused, epidermide tenui cincta ; spiraliter tenuissime exaratd, 

 lineis plus minusve distantibus, in medio plerumque evanidis ; 

 spird haud alte umbilicatd, intus striulis transversis divaric&ta ; 

 labro postice producto ; labio columellam versus rimulam ^l>mb^- 

 licalem simulanie. 



Distinguished by the acuminated form, fine, rather distant 

 spiral grooves, narrow produced aperture, and slight umbilical 

 chink formed by a fold of the labium. The small spiral umbili- 



