350 GASTEROPODA OF THE INFERIOR OOLITE. 
This variety (see Pl. XXTX, fig. 6) is smaller and slightly less depressed than 
average specimens of Ataphrus levigatus. It is, I have no doubt, the form 
identified (‘ Quart. Journ. Geol. Soe.,’ vol. ix, p. 326) as Trochus Belus from Ponton. 
Extremely abundant also at Weldon. ‘The denticle is usually more conspicuous 
than in the accompanying figure, where indeed it is scarcely noticeable. 
284, ATAPHRUS OBTORTUS, Sp. nov. Plate XXIX, figs. 7 and 8. 
Description : 
Width or basal diameter’. : . 1O0—14 mm. 
Width to height . ne Osos 
Shell smooth, thick and gibbous ; spire inedoratcly depressed, and consisting of 
about four or five whorls, of which the penultimate exhibits a remarkable bulge in 
the anterior portion. Aperture circular and small, with a thick denticle on the 
columella, succeeded anteriorly by a shallow pit. 
Relations and Distribution.—In many places where Ataphrus levigatus occurs 
this form may also be noticed, though in fewer numbers. It is probably nothing 
more than a gibbous variety of the common form. I recognise specimens of 
Ataphrus obtortus from Dundry, Beaminster, Mapperton, Stoford, and also from the 
Parkinsoni-zone of Burton Bradstock; also in the Dogger. The interest consists 
in the fact that this species gradually shades off into less depressed forms, which 
are difficult to separate from gibbous varieties of At. Aemon. 
985. Arapurus Lapapyst, d’ Archiac, 1843. Inferior Oolite varieties. Plate XXIX, 
figs. 9 and 10. 
1843. Trocuvs Lapapyet, d’Archiac. Mém. Soe. Géol. France, vol. v, pt. 2, 
p- 379, pl. xxix, fig. 2. 
1850. Turzo Lazapyet, d’Arch. D’Orbigny, Prod., i, p. 301. 
1851. Monopvonra Lapapyert, d’Arch. Morris and Lycett, Great Ool. Moll., 
pt. 1, p. 68, pl. xi, fig. 2; and var., fig. 11. 
1884. Avapurus Lazapyer, d’Arch. Cossmann, Etage Bath., p. 279, pl. vii, 
figs. 5—8. 
Cf. also 2? Monoponta Lavicata, Miinst. Goldfuss, Petref. Germ., pl. excv, fig. 5. 
Curysosroma Acmon, Laube (non d’Orb.). Gast. Br. Jura von Balin, p. 13, 
pl. iii, fig. 2. 
Turzo (Monoponta) Lzviaatus, Sow. ; var. BELLULATA, Bean. Hudleston, 
Geol. Mag., dee. 3, vol. ii, p. 53, pl. ii, 
fig. 4. 
