94 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



perpendicularly costated, tuberculated or spiued ; the last volution cylindrical, sometimes 

 contracted at the base; aperture entire, orbicular or ovate, the lips elevated, produced 

 and slightly thickened, sometimes undulated, columella solid. 



Allied to Cerithium, Potamides, Turritella, Omphalia, Rissoa, and Aclis ; from the 

 two former it is separated by the absence of an anterior and posterior canal, the thickened 

 and produced margins of the aperture distinguish it from Turritella, and from the 

 Omphalia of Zekeli, from Omphalia more especially by the absence of a sinus or fissure 

 of the outer lip, from Rissoa by the many-whirled figure and produced lips, from Aclis 

 by the costated or spined volutions, cylindrical last volution, and produced aperture. 



The Great Oolite species obtained in the Minchinhampton district are always small 

 and sometimes minute, these are Cerithium (?) spicidum. Lye, p. 9; C. (?) strangulatum 

 D'Arch., p. 8 ; C. (?) pulchrum, Lye, p. 10, of which latter species very fine and large 

 examples occur also in the Porest Marble clays of Laycock, accompanied by Kihertia 

 formosa, Lye. Other examples, known only in foreign localities, are Rissoa (?) elegantula, 

 Piette, from the Great Oolite of Eparcy ; Cerithium angistoma, C. quinquangulare and 

 C. pupoides, Hebert and Deslongchamps, from the Kelloway Rock of Montreul-Bellay ; 

 Scalaria {?)minutaand Cerithium pygmeum, Buvignier, from the Calcaire a Astartes of the 

 department of the Moselle. In selecting a name for this proposed genus, I have much 

 pleasure in adopting the suggestion of Mr. Walton, and dedicate it to the memory of the 

 late John Kilvert, Esq., of Bath, whose researches in the Palaeontology of the Jurassic 

 rocks of the southern counties resulted in the acquisition of a fine and instructive 

 collection of the Mollusca. 



KiLVERTiA PULCHRA, Lyc. Tab. XLIV, fig, 4 ; Tab. XLI, figs. 12, 12 a. 



Cekitiiium? pulchrum, p. 10, of this Supplement. 



The fine collection of Forest Marble shells forwarded by the kindness of Mr. Walton, 

 contains many specimens of this Kilvertia which exhibit much variability in their orna- 

 mentation, and are upwards of three times the linear dimensions of the Minchinhampton 

 examples ; the Laycock shells having been obtained by washing layers of clay and shale ; 

 there is an entire absence of that abrasion of the surface to which oolitic fossils have so 

 frequently been subjected ; additional figures of this fine species will be found Tab. XLI, 

 figs. 12, 12 <2. The figure of the aperture in shells of the same size also presents some 

 variability, the typical suborbicular figure becomes sub-quadrate, and in other instances is 

 somewhat pointed at the two extremities, but in the young condition apparently the 

 aperture is always orbicular. 



