366 MOLLUSCA. FISSURELLADtE. Scissurella. 



3. E. Iricarinata — Conical, with the apex bent down ; surface marked with 

 three principal, and several lesser ribs, the spaces between them nearly 



smooth ; base oblong — Soiver. Min. Conch, t. Dxix. f. 2 In Oolile at An- 



cliff. 



4. E. scalaris — Conical, ribbed ; apex excentric ; ribs many, connected by 



numerous cross lines ; base obovate Smcer. Min. Conch, t. Dxix. f. 3. — In 



Oolite at Ancliife. 



Gen. XC. SCISSURELLA.— Shell with a depressed spire; 

 the outer-lip notched with a deep slit, following the 

 growth of the volutions, obliterated to ^vithin a short dis- 

 tance of the margin, and forming a sort of keel upon the 

 back of the shell. 



365. S. crispata. — Transversely ribbed, and spirally striated ; 

 inner-lip reflected on the body-whorl. 



In shell-sand at Noss, Zetland, after a storm. 

 Breadth about the fifteenth of an inch ; white, and without any apparent 

 cuticle : whorls three, increasing rather rapidly from the slightly elevated 

 apex, and sloping, with a gentle convexity, from the separating line to the 

 keel ; under side with a central cavity, from which the whorl extends, a lit- 

 tle convex, to the keel. The whorls are marked by numerous fine trans- 

 verse arcuated ribs, narrower than the intervening spaces, crossed by fine 

 longitudinal striae (most conspicuous in the spaces), giving to the shell its 

 peculiar reticulated appearance ; the ribs on the upper side are coarser than 

 those below. The aperture is suborbicular, slightly depressed, the outer-lip 

 thin ; the inner-lip slightly reflected over the cavity, spread on the body- 

 whorl, and continuous with the outer-lip. From the pillar-cavity a shallow 

 gutter extends anteally, and joins tlie pUlar-lip ; this is chiefly conspicuous 

 on the largest specimens. The longitudinal slit in the middle of the outer- 

 lip extends backwards about two-thirds of the diameter of the shell, where it 

 joins the narrow groove in the keel of the shell which it had formerly occu- 

 pied. The mai'gin of the slit is slightly elevated, as well as the groove, 

 which is seen winding round the whorls at the separating line, nearly to the 



apex ; the groove itself is slightly ribbed across I found this shell in 1809, 



and specimens then transmitted to Mr Montagu, were pronounced by him 

 tiie fr}^ of a Trochus. It is, however, a well marked shell, and belongs to 

 the genus Scissnrella of M. D'Orbignv. 



