94 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
perpendicularly costated, tuberculated or spined; 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 (2) spiculum, Lyc., p. 9; C. (?) strangulatum 
D’Arch., p. 8; C. (?) pulchrum, Lyc., p. 10, of which latter species very fine and large 
examples occur also in the Forest Marble clays of Laycock, accompanied by Kzvertia 
formosa, Lyc. Other examples, known only in foreign localities, are Lvssoa (?) 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 (2) minuta and Cerithium pygmeum, Buvignier, from the Calcaire 4 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 Paleontology of the Jurassic 
rocks of the southern counties resulted in the acquisition of a fine and instructive 
collection of the Mollusca. 
Kinvertia putcura, Lyc. Tab. XLIV, fig, 4; Tab. XLI, figs. 12, 12 a. 
Cerituium? 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, 12a. 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 1s 
somewhat pointed at the two extremities, but in the young condition apparently the 
aperture is always orbicular. 
