418 Mr. R. Tate on a new Genus o/'Cerithiacla3. 



base rounded, with about three ench-cling ribs ; suture deep 

 and narrow ; aperture orbicular ; canal indistinct. 



Total length ^ inch. 



Locality. Zone oi Ammonites Jamesoni: LeckhamptonE-oad, 

 clay-pits, Cheltenham ! [R. T.) ; Aston Magna ! [J. Slatter) ; 

 Camjxlen ! (P. B. Brodie). 



Eustoma is another genus of Cerithiadie founded also by 

 Piette (1855), and in the young state resembles a CeritJiium] 

 but in the adult the margins of the aperture are much ex- 

 panded and posteriorly united by an indistinct canal ; the 

 anterior canal is elongated. It includes E. tuberculosa^ Piette, 

 and E, rostellaria^ ( Gerithiuni) Buvignier, both from the Great 

 Oolite of Ardennes. 



Fibula, a third genus of the family, founded by Piette (1857), 

 is typically represented by Turritella Boissyi, D'Archiac, and 

 presents characters intermediate and approximating it to 

 Turritella and to Ceritliium. The shell is elongated, with a 

 straight columella and a rudimentary groove near the base ; 

 outer lip arched and slightly notched at the suture. Twenty- 

 one species, ranging from the Trias to the Cretaceous, belong 

 here ; the British forms are F. variata and F. eulimoideSy 

 Lycctt, from the Great Oolite of Gloucestershire. 



There remains at the least another well-marked group of 

 Cerithioid shells, Avhich appear to differ much from Cerithiurrij 

 and have been referred to that genus and to Turritella ; they 

 present a characteristic ornamentation, have the aperture 

 rather of Chemnitzia, and the posterior canal of Cerithium. 

 These I propose to arrange under a new generic title. 



Ceyptaulax, nov. gen. 



( CryptoSj hidden ; and aulax, a furrow, in allusion to the pos- 

 terior canal more or less concealed by the outer lip.) 



Type, Cerithium tortile, Hebert & Deslongchamps, Bull. See. 

 Linn, de Normandie, vol. v. (1860) t. 6. f. 1. 



Shell turriculated, pointed, with a polygonal spire, orna- 

 mented with transverse costre ; angles of whorls disposed in a 

 more or less marked spiral series ; imperforate ; columella 

 straight, thin ; aperture ovate, not produced into a distinct 

 canal in front ; peristome entire, broadly retlexcd upon the 

 left lip ; a shallow oblique posterior canal in the angle formed 

 by the body-whorl and outer lip. 



Messrs. Ilebert and Deslongchamps state that the canal of 

 this species is so little pronovmccd that it might be referred to 



