MAZATLAN UNIVALVES 173 



225. Bulla Pnebulosa, Gould. 



U. S. Expl. Exp. Moll— Mice, in Zeli. f. 3Ial. 1850, p. 162, 



no. 2. 



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

 nmbilicus, which are undistiagnishable from the young of B. 

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

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

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

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

 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, soHdity, and 

 size of umbilicus. The adult shells are sufiiciently distinct. 

 Long. 1', lat. '7. 

 Sab.— 8ta. Barbara, Nuttall. — ^&n Diego, Lieut. Green.— 



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



— PDo. jun. extremely rare ; L'pool Col. 



Tablet 788 contains the most characteristic specimen. 



226. Bulla PQugtii, Gray. 



Sow. Thes. Conch, 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 umbiHcus, 

 at an angle of about 60°. Umbihcus strongly striate, bounded 

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

 J3a6.— Gallapagos, Cjmz«7. — ? 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. 2>arvci, ellipticd, compressd, aperturii elo-ngata, angusta ; 

 fused, epiclermide tenul cinctd ; sjnraliter tenuissime exaratd, 

 lineis plus minusve distantihus, in medio plerumque evanidis ; 

 spird liaud alte umhilicatd, intus striulis transversis divaricatd ; 

 lahro postice 2}>'oductG ; lahio columellam versus rimulain nmbi- 

 licalem simulante. 



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 umbUi- 



