TROCHOTOMA. 445 
Genus—Trocnotoma, Deslongchamps, 1842. 
* Shell trochiform, conical or depressed ; base infundibuliform ; whorls but slightly 
convex, keeled ; sinus band obliterated up to the lip, with the exception of an oblong 
fissure, choked in the middle, bipartite; aperture subquadrangular, oblique; lip 
simple and without slit; columellar lip deeply sunk in the false wmbilicus, entire, 
sinuous.” —FIscHER. 
Specimens in our Inferior Oolite, which exhibit the more interesting characters 
of this genus, such as the strangulation of the fissure, and the sinuous or toothed 
character of the columellar lip, are exceedingly rare. This partly arises from the 
false umbilicus being plugged up with matrix. The toothed character of the 
columellar lip is well shown in a specimen of Trochotoma Lindonensis, from 
Lincoln (Pl. XLI, fig. 9). Fischer in 1885 constituted the section, Didymodon, on 
this feature, the type being T'rochotoma quinquecincta, Zieten, from the Corallian 
of Nattheim, which in many respects resembles the Lincoln specimen. 
The genus 7’rochotoma in this country is mainly confined to the Lower Oolites, 
being most abundant in the Bathonian section. The lowest horizons of our Inferior 
Oolite in Dorsetshire contain some forms which in Normandy are quoted from 
the Lias, such as Trochotoma gradus. We may admit that 7’. gradus, T. affinis, 
and 7’. caliv are little more than varieties of one tabulate form. 
386. Trocnoroma cauix, Phillips, 1829. Plate XLI, figs. 1 a, 1b, variety from the 
Cotteswolds, approaching 1’. affinis, 
Deslongchamps; figs. 6a, 6b, 6c, 
typical form from the Dogger; fig. 7. 
1829. Sonarium catrx, Bean, MS. Phillips, Geol. Yorks., pt. 1, p. 157, pl. xi, 
fig. 30. 
1854. Trocuotoma catyx, Phillips. Morris, Cat., p. 280. 
1875. —_ —- — Geol. Yorks., pt. 1, 3rd edit., p. 259. 
1885. — caLix, Phillips. Hudleston, Geol. Mag., dec. 3, vol. ii, 
p- 156, pl. iv, figs. 6, 6a, 60. 
Non Prevroromarta catix, d’Orbigny. Terr. Jur., vol. ii, p. 476, pl. ccclxxxiii, 
figs. 6, 7. 
Bibliography, §c.—On the view that we should separate 17’. calix from T’. gradus 
and 1’. affinis, the synonymy given by me in the ‘ Geol. Mag.’ is too comprehensive. 
The type specimen of Solariuwm caliv is not, I believe, to be found at York, 
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