GASTEROPODA. 37 
CrriteLita. Vov. Gen. 
C. Testa turrita, spird acutd, subulatd, anfractibus planis, marginibus sepissimeé sulcatis ; 
anfractu ultimo amplo ; apertura elongata, obliqud (canali (?) brevissimd) columella levigatd, 
rotundata ad basim subreflead. 
Shell turreted, spire acute, subulate, volutions flattened, their margins usually sulcated ; 
the last whorl large, aperture lengthened and oblique, canal very short ; columella smooth, 
rounded, and slightly reflected at the base; outer lip thin. 
This genus is constituted to receive several species of subulate univalves, usually smooth, 
but sometimes sculptured longitudinally, which seem to be equally removed from Zeredra 
on the one hand, and Cerithiwm on the other; from the genus Fusus they are still more 
remote. ‘The increased size of the last whorl, together with the elongated narrow aperture, 
detach it from the Cerithiz ; neither has it the decided twist of the columella, which we 
find in Zerebra; the base never terminates in a notch, but in a narrow, very short, 
channel, which is turned slightly forwards and outwards ; the whorls are generally flattened, 
the length of the spire exceeding that of the aperture. 
The Certtelle, from their individual number and variety of species, constitute an 
important group in the Great Oolite univalves. The delicacy of the outer lip is such, that 
a specimen with that part perfect has scarcely ever been obtained, the remaining portion 
usually giving to the base the aspect of a short channel, slightly directed outwards. It is 
certain, however, that in several of these species the base of the aperture is very narrow, 
and slightly twisted, approaching nearly to the channelled form, a character which, together 
with that furnished by the spire, separates it sufficiently from the Acfeonine properly so 
called, and to which some of the species have a slight resemblance. We have, therefore, 
provisionally arranged these shells in this part of the series, until the characters of the 
aperture are more fully developed. 
Crrivetia acuta. Plate V, figs. 17, 17a, 18, 18a. 
C. Testa turritd, levigatd ; spird elatd, acutd ; anfractibus (6) convexiusculis ; apertura 
obliqua angustatd, caudd recurvd brevi. 
Shell turreted, smooth; spire elevated, acute; whorls (6) rather convex, aperture 
oblique, narrow ; canal recurved and short. 
The figure of this species varies considerably. The young shells are usually the most 
subulate. The length of the last volution is generally half that of the entire shell. Axis 
10 lines, transverse diameter 4 lines. 
Locality. Yt is numerous in all the shelly beds in the vicinity of Minchinhampton. 
