80 FAUNA OF THE CORNBRASH. 



scarcely possible, however, to deny the similarity, if not the identity, of the fossil 

 from the Dogger. We seem to be able to trace a very instructive history here. 

 The species came from the north, and in Inferior Oolite times reached as far as 

 Yorkshire. In Great Oolite times it did not retire to the south, but out of the 

 country. With the new and wider expansion of strata in Cornbrash times it 

 returned and spread beyond the confines of Yorkshire at least as far as Bedford, 

 and later on, as A T . calypso, it appears to have spread as far as the Ardennes. 

 During its wanderings it gradually became thinner. 



Natica montreuilensis, Heb. and Desk Plate VIII, figs. 4, 5. 



1860. Natica montreuilensis, Hebert and Deslongchamps, Bull. Soc. Linn. Normand., vol. v, p. 31, 



pi. ii, fig. 2. 

 1863. Neritopsis archiaci, Lycett, Suppl. G-. O. Moll. (Pal. Soc), pi. xxi. fig. 7, p. 21. 

 1884. — canaliculata, Hudleston, Geol. Mag. [3], vol. i, p. 301, pi. ix, fig. 12. 



? 1863. Natica texata, Lycett, op. cit., pi. xlv, fig. 30. 



Type. — " Length 14 mm., breadth of last whorl 12 mm. Shell globular, the 

 spire not much projecting, smooth throughout, apex obtuse. Whorls rounded. 

 Sutural furrow well marked and rather deep. Last whorl larger than the rest. 

 Base very oblique. Umbilicus scarcely apparent." From the Callovian beds of 

 Montreuil-Bellay. 



Description. — The shells referable to this species agree in every respect with 

 the above definition with the exceptions to be noted, and they have somewhat 

 the aspect of the same, which is that of a Nerita, the spire being so short and so 

 few-whorled (3-4). Many of them are " smooth throughout," but the best 

 preserved show numerous longitudinal bands like flat folds crossed by over-riding 

 narrower and closer festooned spirals without interfering with the visible smooth- 

 ness. The umbilicus is small, but perfectly distinct. The inner lip and basal 

 part of the aperture is thicker than the outer lip. There are patches of black and 

 yellow colour like clouds in the shell, and some retain a black incrustation in a 

 separate layer, which may be the remains of an epidermis. The fossils mostly retain 

 their shell in Yorkshire, being there thoroughly autochthonous. The shell is thick 

 so that in casts the whorls are nearly separate. 



Distribution. — From their home in Yorkshire seven specimens have been obtained, 

 and one from Stow-nine-Churches, also casts from Bedford (2), Hullavington, and 

 Holwell. 



Relations. — It is curious that this shell should have passed muster so long as a 

 Neritopsis. The specimens only required development. It then appears that the 

 whorl continues round the columella and there is no callous plate — much less a 

 notch in it. 



