POETIAND EOCKS OF ENGLAND. 229 



Alaeia Beatjgrandi, De Loriol. 



This is a well-marked species, with two strong keels on each 

 whorl, of small size, and pretty common in the creamy limestones 

 of Bucks. See Mem. Soc. !N^at. et Phys. de Geneve, torn, xxiii. pi. ix. 

 fig. 19. 



Natica ceees, De Loriol. PI. IX. fig. 2. 



This characteristic species is well marked by its acute spire, well- 

 separated whorls, and deep, almost ornamental lines of growth. 

 The British specimens are perfectly consonant with the author's 

 figures and description. 



Natica incisa, spec. nov. PI. IX. figs. 1, la. 



This is very nearly allied to iV^. ceres, with which it is found 

 associated. Its distinguishing characteristic is a broad depression 

 running longitudinally along the upper part of the whorl, so that 

 the top and middle line are swollen. There are deep, subornamental 

 lines of growth ; and these are crossed by closer-set fine longitudinal 

 lines. The spire is short and not very acute. The umbilicus is 

 moderate in size. iV. ceres shows slight traces of a longitudinal de- 

 pression and lines ; but in this they are so marked as to render the 

 shell more like Neritoma sinuosa. 



In the creamy limestones at Coney Hill and Quainton, rather 

 common ; also in the Portland Sand, Portland. 



Cerithium IItjdlesto:ni, spec. nov. PI. IX. fig. 3. 



This has an apical angle of 17° ; and five whorls are visible ; they 

 are only moderately convex and slightly separated. The ornaments 

 are on the upper half of each whorl {i. e. nearer the apex) ; transverse 

 ribs, thirteen in number, in the last two whorls ; these have a gentle 

 convexity backwards, and die off at each end, leaving the lower half 

 uncovered. This has three sharp longitudinal lines ; and four more, 

 parallel to them and finer, cross the ribs. The base is covered by 

 the longitudinal lines only. Length 4| lines. This is nearly allied 

 to C. septemplicatum, and is probably the same as De Loriol's exam- 

 ples figured in the ' Bulletin de la Soc. Sc. Hist. Xat. de I'Tonne,' 

 2nd ser. tom. i. pi. iii. fig. 4 ; but the ribbing and folding of Eomer's 

 species is much more regular. 



In the creamy limestones of Coney Hill and Hartwell. 



Ceeitketjm blpuecatum, spec. nov. PL IX. fig. 5. 



Apical angle 24°, whorls rather inflated, sutures distinct, last 

 whorl, not including the beak, half as large again as the penulti- 

 mate. Ornaments about eighteen elevated transverse ribs with a 

 slight convexity backwards, strongest towards the top. Halfway 

 across the whorl they give place to two smaller ones, one being the 

 continuation of the original. These are all knotted by longitudinal 

 lines of alternating strength, about eight in number. The base has 

 only knotted longitudinal lines. Total length about ^ inch. This 



