96 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



tions, which have a prominent encircling nodiferous carina in their middle portion, their 

 posterior and anterior surfaces being concave, each having a small noderous carina ; the 

 last volution has at its base fine encircling sulcations; the aperture has the anterior 

 extremity rather pointed. 



The tubercles upon the mesial carina are large, projecting slightly forwards, very 

 closely arranged and tubular, about eighteen in a volution, the anterior and posterior 

 carinaa have similar tubercles, but much smaller. The height of the shell is one third 

 greater than the opposite measurement. 



Geological Position and Locality. The Forest Marble of Laycock ; in the collection of 

 W. Walton, Esq. 



AMBERLEYA TRICINCTA, Lye. Tab. XLI, fig. 14. 



Testa ovato-elongata, anfractibus (8 9) turbinatis, inferne angulatis, citigillis, tribus t 

 lineis perpendicularibus decussatis, anfractu ultimo, lineis maynis concentricis ; apertura 

 pyriformi. 



Shell ovately elongated, volutions (8 9 turbinated, angulated towards their lower 

 portions, and flattened or slightly convex above the angle, the sutures are strongly marked, 

 encircling lines three, of which one is above and another beneath the angle ; these are 

 decussated by other lines perpendicular and smaller, forming tubercles more or less distinct 

 where they cross the angle, the decussating lines are distantly and sometimes irregularly 

 arranged ; the last volution has large, regular, concentric elevations ; the aperture is 

 pyriform. 



An elegantly turbinated more or less lengthened shell, with convex volutions and a 

 delicately ornamented surface ; about a dozen specimens have been compared, which do not 

 vary much in size ; the length of the aperture is about two fifths of the entire shell. All 

 the examples are more or less imperfect at the base. 



Geological Position and Locality. The Forest Marble of Laycock ; in the collection 

 of W. Walton, Esq. 



NATICA TEXATA, Lye. Tab. XLV, figs. 30, 30 a. 



Testa ovata, dcpressiuscula, crassa, spira anfractibus (3) patens, vix elevatis, convexis ; 

 anfractu ultimo inflato, basi umbilicato, apertura subreniformi, labro inferno crasso ; svperficie 

 striis vel lineis texatis delicatissimis ornata. 



Shell ovate, depressed, thick, spire consisting of three depressed but exposed and 

 rounded volutions, the last volution much inflated, the base umbilicated, the aperture 

 somewhat reniform, the inner lip thick and conspicuous ; the surface with very delicate 

 encircling lines or striations, which are rendered granular by others decussating them. 



