182 MOLLUSCA FROM THE CRAG. 



4. BuLL^A VENTROSA. *S'. Wood. Tab. XXI, fig. 11, a — c. 



Bulla ventrosa. S. Wood. Illust. in Mag. Nat. Hist. p. 462. pi. 7, fig. 5, 18.39. 

 _ S. Wood. Catalogue 1842. 



B. Testa pusilld, crassd, ventrosa, ovato-ylohosd ; spird occulta ; aiifracfi/jus paucis, 

 oljliqiiis, laxe convolutis, superne vix coarctatis, striatis ; striis diver (lentihus, excavato- 

 punctafis ; aperturd ovali, inferne patente, dUatatd ; lahio prominente, pone umbilicato. 



Shell small, strong, ventricose, ovato-globose ; spire concealed by the elevation 

 of the outer lip ; volutions few, slightly enrolled, covered externally, with numerous 

 regular, punctured, and diverging strife : body of the whorl slightly contracted on 

 the upper half; aperture ovate, somewhat contracted above, expanded below ; inner 

 lip prominent, slightl}^ reflected, with a small umbilicus behind it. 



Axis, I of an inch ; diameter, \. 



Localitij. Cor. Crag, Sutton. 



I have obtained only a few specimens of this shell. It somewhat resembles a minute 

 B. lignuria, but it has an umbiUcus, and is otherwise distinct. My specimens appear 

 to have punctured lines, and not chain-like striae on the exterior ; but they may, 

 perhaps, be in an altered condition. This may possibly be Bulla zonata, Turt. Mag. 

 Nat. Hist. 1834, p. .352, but the croiATi of our shell can scarcely be said to be 

 umbilicated ; the outer lip is deeply cleft or sinuated, and disconnected up to the 

 vertex ; and the replication of the inner lip forms a distinct umbilicus. There is a 

 deep muscular impression running nearly parallel with the outer lip, which is regular 

 and continuous the whole length of the shell. 



Ord. CYCLOBBANCHIATA. Cuv. 

 Patell.\. Linnmis. 1758. 



Gen. Char. Shell conical, clypeiform, with an oblong or ovate base ; apex or 

 vertex subcentral, always more or less on the anterior portion ; generally rayed, 

 striated, or costated, with a crenulated margin, occasionally smooth; muscular 

 impression, a ligulatc band surrounding the interior, about half way up, open in front 

 tor the head of the animal. 



Animals of this genus differ from the fissured and keyhole limpets in having the 

 branchiae on the outer edge under the margin, and have, in consequence, been placed 

 in a different order. Wlien living, the edge of the shell is generally slightly raised 

 from the rock, to admit the water to the branchise, and the blade of a knife can easily 

 be passed under the margin of the shell, if undisturbed ; but when alarmed, the water 



