418 Mr. R. Tate on a new Genus o/" Cerithiadse. 



base rounded, with about three encircling ribs ; suture deep 

 and narrow ; aperture orbicular ; canal indistinct. 



Total length ^ inch. 



Locality. TaOxvq oi Ammonites Jamesoni'. LeckhamptonRoad, 

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

 Campden ! (P. B. Brodie). 



Eustoma is another genus of Cerithiadee founded also by 

 Piette (1855), and in the young state resembles a CeritMum ; 

 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^ ( CeritMum) Buvignier, both from the Great 

 Oolite of Ardennes. 



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

 is typically represented by Turritella Roissyi^ D'Archiac, and 

 presents characters intermediate and approximating it to 

 Turritella and to CeritMum. 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. eulimoides^ 

 Lycett, from the Great Oolite of Gloucestershire. 



There remains at the least another well-marked group of 

 Cerithioid shells, which appear to differ much from CeritMum^ 

 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 CeritMum. 

 These I propose to arrange under a new generic title. 



Crtptaulax, nov. gen. 



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

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



Type, CeritMum tortile, Hubert & Deslongchamps, Bull. Soc. 

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



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

 mented with transverse costge ; 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 reflexed upon the 

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

 by the body-whorl and outer lip. 



Messrs. Hubert and Deslongchamps state that the canal of 

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



