ATAPHRUS. 349 



283. Ataphrus l^vigatus, Soiverby, 1818. Plate XXIX, fig. 5; and variety ap- 

 proaching A. Belus, d'Orb., fig. 6. 



1818. Neeita l.£vigata, Sowerby. Min. Conch., pi. ccxvii, fig. 1. 



1853. Monodonta l.evigata, Sow. Lycett, Proc. Cotteswold Nat. Club, vol. i, 



p. 71. 



1854. — — — Morris, Cat., p. 258. 



1873. — — — Tawney, Dundry Gasteropoda, p. 34 (26). 



1885. Tuebo (Monodonta) ljbvigatus, Sow. Hudleston, Geol. Mag., dec. 3, 



vol. ii, pi. ii, fig. 6. 

 Cf. also Monodonta ovulata, Heb. and Best. Op. cit. 



Chetsostoma ovulata, Heb. and Besl. Laube, Cast. Br. Jura von Balin, 



p. 13, pi. iii, fig. 3. 



Bibliography, Sfc. — Sowerby's figure is far from being characteristic, as he 

 remarks that " the specimens do not exhibit the columella." Had this been other- 

 wise he would hardly have taken his fossil for a Nerite. Mr. Tawney thought that 

 Sowerby's type was in the Bristol Museum. With reference to this point Mr. 

 Wilson, the present Curator, wrote in 1893, " The types do not appear, after all, to 

 be at Bristol. Our tablet of specimens, so classed, probably gives a good exem- 

 plification of Sowerby's species." With this latter remark I quite agree; in the 

 majority of these specimens the denticle is conspicuous. 



Description : 



Width or basal diameter . . 12 — 14 mm. 



Width to height . . . 5:4. 



Shell globular, smooth and thick ; spire moderately depressed ; number of 

 whorls about four ; last whorl ventricose, with sometimes a slight posterior 

 flattening ; sutures close. Aperture circular and small, with a strong columellar 

 callosity or denticle, associated in some cases with a faint columellar furrow or pit. 



Relations and Distribution. — This is the most common form of Ataphrus in the 

 Inferior Oolite, and may be regarded as the representative of the turbinate section, 

 where the spiral angle, as far as it can be determined in such obtuse shells, exceeds 

 90°. There is considerable variety ; or, what amounts to the same thing, we are 

 content to place a certain range of forms under one specific designation. These 

 differences are greatly accentuated by the state of preservation, which varies 

 considerably according to the nature of the deposit. 



The finest and most characteristic specimens occur at Dundry ; but it is to be 

 met with, more frequently perhaps on a low horizon, in many parts of the Inferior 

 Oolite from Dorset to Yorkshire. 



Variety va the Lincolnshire Limestone. Cf. Trochus Belus, a" Orb., ' Terr. Jur./ 

 vol. ii, p. 283, pi. cccxv, figs. 9 — 12. 



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