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 poimted. 
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 
carinee 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, Lyc. Tab. XLI, fig. 14. 
Testa ovato-elongata, anfractibus (83—9) turbinatis, inferne angulatis, cingillis, tribus, 
lineis perpendicularibus decussatis, anfractu altimo, 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 distinet 
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 rexata, Zyc. Tab. XLV, figs. 30, 30a. 
Testa ovata, depressiuscula, crassa, spira anfractibus (3) patens, viz elevatis, convezis ; 
anfractu ultimo inflato, basi umbilicato, apertura subreniformi, labro interno crasso ; superficte 
struis vel liners 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. 
