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I.—Contributions to the Palæontology of the Yorkshire Oolites

Published online by Cambridge University Press:  01 May 2009

Wilfrid H. Hudleston
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Extract

The subject of the identity of the great shell (or rather cast), which occurs in the Scarborough Limestone, with the Corallian P. striata, was partly discussed in the “Corallian Gasteropoda.” The considerable abundance of this form on certain horizons in the Oolites, both of the north and south of England, and its complete absence from other horizons, has attracted considerable attention. Thus it appears alike in the Humphresianus-zone of Scarborough and of Cheltenham, but not, as far as I know, in lower beds. The Yorkshire specimens are not good enough to warrant any conclusions as to the specific difference between this and the Corallian forms; therefore it seems safer to follow the authors of the Great Oolite Mollusca in referring the White Nab fossils to Sowerby's species. Moreover, I have less doubt as to the propriety of this course after reading the very interesting remarks of MM. Terquem and Jourdy with reference to Bourguetia striata.

Type
Original Articles
Information
Geological Magazine , Volume 1 , Issue 2 , February 1884 , pp. 49 - 63
Copyright
Copyright © Cambridge University Press 1884

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References

page 49 note 1 p. 23 of separate memoir.Google Scholar

page 50 note 1 1850. Phasianella latiuscula, Morr. and Lye. Gt. Ool. Moll. p. 117, pi. xv. fig. 16.Google Scholar

These authors describe and figure a fossil cast, stated to occur “near Scarborough,” under the above designation. Their figure is very familiar to Jurassic palæontologists, and has a certain resemblance to the soi-disant Phasianellas, of which several species occur in the Bathonian Beds of the West Midland district. In the Leckenby Collection there are no specimens which could fairly be referred to Morris and Lycett's species, except such as have a strong resemblance to Natica Bajocensis {N. punctura, Bean, Inf. Oolite variety). The specimen in the York Museum referred to, “P. latiuscula” is exactly like Morris and Lycett's figure, being a very perfect internal cast of a Naticoid shell in the grey matrix of the Scarborough Limestone, and having considerable resemblance to the shell of P. elegans, a species of the Great Oolite of the West Midlands. But it is certainly misleading to institute a comparison between the external form of one shell and the internal mould of another, even in the case of unornamented species.

The ratio between the body-whorl and the whole spire in the cast known as “P. latiuscula”, is as 50:100; in average forms of the shell of Natica Bajocensis this ratio may be taken as 60:100. Making due allowance for the difference which is certain to exist between the external proportions of a shell and those of its internal moulds, it is by no means impossible that “P. latiuscula” represents the cast of Natica Bajocensis.

As it may be necessary to publish a supplemental plate at the end of this Memoir, I shall be very glad if any proof can be adduced in the mean time of the occurrence of such a species as “P. latiuscula, as a distinct shell.

page 51 note 1 It should be borne in mind that the Dogger Sands are classed as part of the Upper Lias by some authorities, though not by Tate and Blake, who enumerate eight species of Cerithium from the entire formation, not including these Sands. Again, the division between the Dogger and the Dogger Sands at Blue Wyke may be drawn somewhat differently. This subject has been discussed by me at some length in the first part of the “Yorkshire Oolites” (Proc. Geol. Assoc. vol. iii.Google Scholar), where it was pointed out that, besides the Nerinæa-bed which yields the bulk of the specimens classed as “from the Dogger,” there are three fossiliferous beds below this which form a part of the Dogger proper. The irony condition of the Nerinæabed and its shells is generally a pretty safe test as to a specimen coming from the Dogger, but this is not in all cases to be relied upon as regards the lower fossiliferous zones, which yet form part of the Dogger and not of the Dogger Sands. Hence there is a possibility in some cases that fossils believed, on account of their matrix and mineral condition, to have come from the Sands, may in reality have been obtained from the lower fossiliferous beds of the Dogger proper.

page 52 note 1 N.B.—It may be worth remarking that in the Chemnitzia vetusta group the longitudinal ornaments are more conspicuous than the spiral ones: in the Cerithium muricatum group the two systems of ornament are about equally strong, whilst in the Turritellæ of the Dogger the ornamentation is altogether arranged spirally.

page 53 note 1 In this measurement the penultimate is selected.

page 54 note 1 Goldf. Gast. p. 30, pi. 173, fig. 11.Google Scholar

page 54 note 2 Q. J. G. S., vol. for 1869, p. 13, pi. 3, fig. 13.Google Scholar

page 55 note 1 Quenstedt, Der Jura, p. 417, pi. 57, figs. 15 and 16.Google Scholar

page 57 note 1 Specimens from this horizon near Weymouth have the longitudinals more closely set, and the whorls are without the constriction towards the base.

page 57 note 2 Quenst. Der. Jura, p. 417.Google Scholar

page 57 note 3 Bull. Soc. Linn. Norm. vol. v. p. 41 (sep. mem.), pl. vi. fig. 2.Google Scholar

page 57 note 4 Vol. crt. p. 38, p1. vii. fig. 1.Google Scholar

page 59 note 1 Quoted as common in the Lincolnshire Limestone, App. to Judd's Geol. of Rutland, p. 281.Google Scholar

page 60 note 1 Op. cit. App. p. 281.Google Scholar

page 62 note 1 No one seems to know exactly where this place is situated.