98 FAUNA OF THE CORNBRASH. 



Cylindrites thorenti (Buvignier). Plate IX, fig. 5. 



1842. Bulla thorentea, Buvignier, G-col des Ardennes, p. 535, pi. v, fig. 9. 



1850. Cylindrites thorenti, Morris and Lycett, Great Ool. Mollusca (Pal. SoiO, p. 101, pi. viii, fig 22. 



Type. — Shell subcylindrical, the sides somewhat convex, smooth, or slightly 

 marked by the lines of growth. Spire small, depressed, and contracted. The 

 whorls with their margin only visible. Aperture narrow. Basal fold of the 

 columella large. Apex large, but not so high as the outer margin. In the white 

 limestone below the Oxford Clay, Rumigiry, Ardennes. 



Description. — The figured specimen referred to this species is 17 mm. long 

 and 8 mm. broad, of the same diameter till near the end. The diameter of the 

 aperture is also constant till near the base, a strong fold is shown on the columella, 

 longitudinal lines of growth on the shell, apex sunk, the last whorl making a high 

 and thickened ring round it. 



Distribution. — There can be little doubt that this is a similar shell to that dealt 

 with by Morris and Lycett. Two specimens have been brought by the Survey 

 from Oorscombe. The only quarry seen there now contains beds underlying the 

 Cornbrash, and the matrix is not very characteristic ; nevertheless, as the species 

 is abundant in the Cornbrash of Boulogne, it might very well occur in the South of 

 England. 



Genus VANIKORO, Quoy and Gaimard. 



" Broadly patulate, rather thick, cancellated with oblique lamellar ribs and 

 thin spiral ridges. Epidermis yellowish-brown." Diameter one inch. 



Vanikoro canaliculata, sp. no v. Plate IX, fig. 9. 



This shell stands obliquely on the animal by the look of it. They are all 

 ridged, most of them are smaller. 



Finn Hi/ Bullion. 



This name is used in its comprehensive sense to include all the remaining 

 Tectibranchs, even if none belong to the genus Bulla, if that genus be defined as 

 having a spire wholly immersed, and lacking all spiral lines of colour. Like as are 

 the Cornbrash shells to Bulla, they pass over by these characters into Hydatina. 



■Genus HYDATINA, Schumacher. 



The genus Hydatina is defined by Pilsbry (Tryon and Pilsbry, 'Man. 

 Conch.,' vol. xv, pt. 4, p. 326) as smooth, spirally banded, spire exposed, either 



