388 GASTEROPODA OF THE INFERIOR OOLITE. 



by axial lines. Base rounded and similarly ornamented. Aperture subquadrate 

 with a columellar furrow. 



Relations and Distribution. — An increase in the strength of the axial orna- 

 mentation would approximate this form to Trochus Niortensis. 



T. marga is most abundant in the Parkinsoni-ma,r\ at Bradford Abbas. It 

 occurs more rarely on the same horizon at Burton Bradstock. 



328. Troohus Niortensis, d'Orbigny, 1852. 



1852. Teochtjs Niobtensis, d'Orbigny. Terr. Jur., vol. ii, p. 282, pi. cccxv, 



figs. 5 -8. 

 1873. — — — Tawney, Dundry Gasteropoda, p. 33(25). 



When Mr. Tawney wrote, there were in the Bristol Museum two specimens 

 from Dundry agreeing precisely with d'Orbigny's description. A third specimen 

 has since been added. Mr. Wilson, the present curator, informs me that this 

 species ranges up from the Middle Lias. The micromorph from the Pea-grit of 

 Leckhampton (PL XXXII, figs. 18 a, 18 b) is related. N.B.— The whorls of this 

 small shell are more concave than is shown in the enlargement. 



329. Trochus, species or variety. Plate XXXII, fig. 16. 



A small, unornamented Trochus, with whorls very much undercut, occurs 

 sparingly at Weldon in the Lincolnshire Limestone. In my Collection this is 

 designated Trochus " subimbricatus." 



330. Trochus cf. Bixa, d'Orbigny, 1850. Plate XXXII, fig. 17 ; and ? Plate XXXI, 



fig. 16. 



1850. Teochus Bixa, d'Orbigny. Prod., 1, p. 300. 



1852. — — — Terr. Jur., vol. ii, p. 287, pi. cccxvi, figs. 13—16. 



Cf. also — Langbunensis, d'Orb. Cossmanri, Stage Bath., p. 289, pi. xiii, 



figs. 24—25. 



Bibliography, fyc. — Specimens from our Inferior Oolite agree so well with the 

 description and figures of d'Orbigny of a shell from the Bathonian of Luc in 

 Calvados that I do not feel justified in separating them, notwithstanding the 

 difference in geological age. M. Cossmann regards T. Bixa, d'Orb., as merely a 

 synonym of T. Langrunensis, d'Orb. ; but as our shells resemble T. Bixa I retain 

 the former name, the more so since the essential feature of spiral striation is 

 entirely wanting in T. Langrunensis — possibly from attrition. 



