16 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



Genus FIBULA, Piette, 1857. 



Description des Cerithmm enfonis dans les depots bathoniens de 1'Aine et des Ardennes, par M. Ed. 

 Piette, 'Bull, de la Soc. Ge'ol. de France," 20 Avril, 1857. 



M. Piette has founded his proposed genus upon a small group of lengthened spiral 

 univalves which possess characters intermediate and approximating them to Turritella and 

 to Cerithium. A rounded, straight columella, with a rudimentary umbilical groove near 

 the base, is combined with an arcuated outer lip slightly notched posteriorly at the suture ; 

 the base of the aperture forms a slight canal at its junction with the anterior extremity of 

 the columella, or in other instances there is no canal, the base being rounded and entire, 

 depending upon the exact period of growth at which the animal perished ; the surface of 

 the volutions is plain, or slightly ornamented with oblique costae. The author has figured 

 and described several species, and has characterised his genus in the following terms : " Le 

 principal charactere du ce genre est d'avoir une columella droite. Le bord libre est arque, 

 legerement echancre a sa partie posterieure, pres de la suture. L'ombilic n'est souvent 

 que rudimentaire, a peine indique, et affectant seulement la columelle externe. D'autres- 

 fois, il penetre tout le spire. Un caractere tres curieux que j'ai remarque sur plusieurs 

 especes de ce genre, mais que je n'ai pu encore constater sur toutes, c'est que la columelle 

 se termine parfois interieurement par un canal rudimentaire ; que le mollusque forme ce 

 canal et le rebouche tour a tour, pour le former ensuite de nouveau en grandissant. 

 . . . . Ainsi il arrive souvent que parmi plusieurs Fibula d'une meme espece, les 

 unes semblent se rapprocher des Cerithium, les autres des Turritettes. Cela depend du 

 moment ou elles ont peri." 



In admitting the generic value of Fibula, it becomes necessary to arrange with it the 

 following Jurassic Testacea : Chemnitzia phasianoides (Mor. and Lye.). Cerithium Eoissii 

 (Mor. and Lye.), Turritella Roissii (D'Arch.), and Cerithium mturale (Buvignier). The 

 Great Oolite of Oxfordshire and of Minchinhampton has supplied the two following 

 additional species. 



FIBULA VARIATA, Lye. Tab. XXXI, figs. 4, 4 a. 



Testa turriculata, subventricosa ; spira elonyata, acuta, leeve, anfractibus (11 12) con- 

 vexiusculis, angustis, suturis valde impressis ; ultimo anfractu symmetrico-curvato ; columella 

 interdum ad basin subcanaliculato, aut integro, labro sinistro arcuato. 



Shell turriculated, somewhat inflated ; spire lengthened, acute, smooth, consisting of 

 11 or 12 narrow, somewhat convex volutions, with deeply impressed sutures; the last 

 volution is conformable with the others, and is symmetrically curved towards its anterior 



