122 W. E. Hudleston—The Yorkshire Oolite. 



granular, that is to say, it consists of a system of transverse ribbing, 

 deeply decussated by longitudinal furrows. Below the last sulcus 

 the granular character is less decided, and the base of the shell has 

 numerous fine spiral lines, which decussate with wavy lines of 

 growth. Base rounded and tumid : aperture subquadrate : um- 

 bilicus, little more than a notch : columella short and sloping. 



Relations and Distribution. — This small variety of Pleurotomaria 

 has features in common with many named forms ; and yet, when 

 closely compared with these, it is not found to fit any of them exactly. 

 In Yorkshire it has only been noted in one locality, whence but few 

 specimens have been obtained. This shell-bed lies towards the 

 base of the Lower Limestones, and on the same local horizon with 

 the Gervillia-heds of Scarborough Castle Hill.^ It is Oxfordian, and 

 contains several of the fossils of the " Oolithe ferrugineuse " of 

 Viel St.-Eemy, etc. 



A very near relation is the Cornbrash species described by Lycett 

 (Supplement to Great Oolite Mollusca, p. 24, pi. 31, figs. 8, 8a) as 

 PL granulata, Sow.^ When we turn to foreign authors, it is clear 

 that the Wydale Pleurotomaria has affinities with the PL Munsteri 

 group, and especially with the variety PL BucJiana, d'Orb. (Terr. 

 Jurass. vol. ii. p. 652, and pi. 417, figs. 6-10). Nevertheless, in 

 this case, although the outline and proportions are very nearly the 

 same, D'Orbigny's fossil from the "Oolithe ferrugineuse" is repre- 

 sented as being more finely marked. Judging, however, from 

 D'Orbigny's figure 8, the base of the two shells is identical. On the 

 ■whole, the Wydale shell may be deemed a dwarf variety of the PL 

 Munsteri group, somewhat diff'ering from any form as yet described. 

 There is a form of about the same size, and with many points in 

 common, which occurs in the shell-bed at Cumnor, near the top of 

 the Lower Calcareous Grit. Thus similarity of physical conditions 



^ It should be borne in mind that the Coralline Oolite of Scarborough Castle is 

 lower geologically than the Coralline Oolite of Malton. 



2 Sowerby's species is a fossil of the Inferior Oolite, originally described (M. C. 

 t. 220, fig. 2) from Dundry. He gives two figures, but does not distinguish them 

 by letter or numeral. The specimens are not in the type collection at the New 

 Natural Histoiy Museum. Nevertheless, since a fossil similar to the right-hand 

 figure is so common in the Inferior Oolite of Bradford Abbas and elsewhere, we 

 cannot be in doubt as to the form of Sowerby's species. That author says that "the 

 granulated surface is the result of decussating furrows which vary in depth and 

 number in different individuals." I have examined a large series of English speci- 

 mens from the Inferior Oolite, and find that Sowerby's F. granulata, though subject 

 to great variety, has a much wider spiral angle, is more umbilicated, and has a 

 greater variety of ornamentation. Nevertheless there are forms in the Inferior 

 Oolite of Normandy classed by Deslongchamps as varieties of P. granulata (see Mem. 

 Soc. Linn. Norm. vol. viii. pi. 16, fig. 6a), which lead up to the Cornbrash species, 

 and also to the foi-m now under consideration. See also a figiu-e in Quenstedt's Der 

 Jiura, p]. 57. fig. 7, of a fossil from the Brauner Jm-a delta, p. 414. Still the 

 elements of the Fleurotomaria in the Yorkshire Cornbrash, which must be regarded 

 as very closely related to the shell now figured, are clearly not those of PI. granulata, 

 Sow., in any respect beyond the granulated character of the general sculptiure. We 

 have seen that Sowerby regarded the granulated surface of his species as the result of 

 decussating furrows varying in depth and number ; hence, when we bear in mind like- 

 wise the great differences in external appearance due to various conditions of mineral- 

 ization, too much stress should not be laid upon mere granulation. 



