GASTEROPODA. 37 



Ceritella. Nov. Gen. 



C. Testa turritd, spird acuta, subulatd, anfractibus plants, marginibus scepissime sulcatis ; 

 anfractu ultimo amplo ; aperturd elongatd, obliqud (canali (?) brevissimd) columella Icevigatd, 

 rotundatd ad basim subreflexd. 



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 Terebra 

 on the one hand, and Cerithium 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 Cerithice ; neither has it the decided twist of the columella, which we 

 find in Terebra; 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 Ceritella, 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 Acteoninee 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. 



Ceritella acuta. Plate V, figs. 17, Via, 18, 18a. 



C. Testa turritd, lavigatd ; spird elald, acuta; anfractibus (6) convexiusculis ; aperturd 

 obliqud 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. It is numerous in all the shelly beds in the vicinity of Miuchinhampton. 



