THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. II. 



No. II.— FEBRUARY, 1875. 



OZEaia-IZLsT-A-Ij ABTICLES. 



I. — On the Gault Aporhbaw^i. 

 By J. Starkie Gardner, F.G.S. 

 (PLATE III.) 



IN this paper I purpose giving a history and description of the 

 Cretaceous group of Aporrhais, as far as they are at present 

 known to me, especially of those forms which are so beautifully 

 preserved in the Gault of Folkestone, and so-called Upper Green- 

 sand of Blackdown. I regret that I cannot include the Aptien and 

 Neocomien species, but the collections at present open to me are too 

 meagre to give anything like a complete account of them. In the 

 whole group there are even now many points which require further 

 research ; the correlation of some of the forms with those on the 

 Continent is still unsatisfactory, from the difficulty experienced in 

 comparing actual specimens. The figures available, even in the 

 most modem works, appear in some cases to have been restored, and 

 not therefore to represent the form of any shell that has been really 

 met with. 



As a result of my examination, I think it very probable that all 

 or most of the British Cretaceous fossil forms are met with in 

 similar deposits abroad; but this uncertainty in figuring, and the 

 practice of describing new species from single and generally imper- 

 fect specimens, has prevented me from placing similar, and what 

 appear closely allied forms under the same specific names. 



I believe the list appended from the Gault at Folkestone to be a 

 complete one, so far as the forms are at present known, as it is 

 based on an examination of many hundreds of specimens. As 

 regards the Blackdown list, I find I cannot confirm the statements 

 of the occurrence of many species mentioned by other writers. I 

 have seen and examined the collections of the British Museum, 

 Geological Museum, Geological Society's Museum, and many private 

 cabinets, with this view, but unsuccessfully. I have also reason to 

 believe that many undescribed species exist from the Upper Green- 

 sand, Chloritic-marl, and Chalk, in cabinets which I have not yet 

 seen, and I shall be obliged to any one who would inform me of 

 them. 



Forbes and Hanley, in the British Mollusca, vol. iii., in 1853, first 

 included Aporrhais with the CeritMadce. They considered them to 

 constitute a group intermediate between the holostomatous and 

 siphonostomatous Pectinibranchiata, and to be closely allied to 

 Turritellidce on one hand, and Scalaridce on the other ; they also state 



DECADE II. — "VOL. II. — NO. II. 4 



