170 GASTEROPODA OF THE INFERIOR OOLITE. 



The body-whorl is about one-third the height of the entire shell, with ornaments 

 similar to those of the spire; there is a faint rim at the base, which causes it to 

 be very slightly carinate at either extremity. Base depressed and ornamented 

 with numerous fine spiral striae. Aperture almost quadrate. Columella short, 

 with a considerable callus ; anterior canal apparently small. 



Relations and Distribution. — This form, or something very like it, occurs in 

 several countries, and on more than one horizon of the Jurassic system. The 

 nearest approach, so far as I am aware, is Cerithium aptyxoides, Gemmellaro, which 

 has nearly the same spiral angle and general proportions, though not quite so 

 " gradate." Moreover, Gemmellaro states that C. aptyxoides has a smooth surface 

 (' Gemm. Faun. Giur.,' &c, p. 290, plate 23, figs. 10 — 12). Cerithium gradatum, 1 

 Hudl., from the Yorkshire Corallian, is also very similar (' Geol. Mag.,' dec. ii, vol. 

 vii, pi. xvi, fig. 5), but this also is without ornament, though possibly the 

 circumstance may have been due to conditions of mineralization. 



Cerithium pergradatum occurs at Haselbury, possibly in the Opalinus-zone, and 

 is extremely rare. 



98. Cerithium (? species). Plate X, figs. 7 a, 7 b. 



Description. — The length of specimens about 5 mm., spiral angle about 16°; 

 shell subulate, spiral angle nearly regular. Whorls about ten in number, smooth 

 and belted posteriorly, so as to form steps. 



Body-whorl scarcely one-third of the total height of the shell, concave and 

 slightly bicarinate. Aperture restricted, subquadrate, with a fairly well-developed 

 anterior canal. The whorls in section are seen to be subcircular to ovate. 



Relations and Distribution. — These little shells occur sparingly in the Lincoln- 

 shire Limestone. Being so small, it is possible that they represent the immature 

 conditions of some other species, described or unknown. Simply as a name of 

 convenience, and awaiting further evidence, I would call this " species " C. " annu- 

 latum." 



99. Cerithium cltpeus, sp. nov. Plate X, figs. 8 a, 8 b, 8'. 



Description. — Length of an average specimen 24 mm., greatest breadth rather 

 more than one-fourth of the length; spiral angle 16°. Shell elongate, turrited. 

 Spiral angle nearly regular, sutures close. Whorls about fourteen, raised posteriorly 

 by a belt which occupies the upper margin, nearly flat ; the increase is by steps, 



1 This name will not stand, since it had been previously applied by Moore to a species of 

 Cerithium in the Lias, which belongs to a different section of the genus. 



