THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE 111. VOL. I. 



No. XII.— DECEMBER, 1884. 



I. — British Eocene ApoKRHAiDiE. 



By J. Stabkie Gardner, F.L.S., F.G.S., etc. 



(PLATE XVII.) 



NEAELY ten years ago it was my pi'ivilege to describe the British 

 Cretaceous forms of this Family in the Geological Magazine. 

 The Family was seen to be capable of subdivision into at least five 

 well-marked genera, and to these a sixth very singular and remark- 

 able one from Aix-la-Chapelle, and also represented at Blackdown, 

 may be added. It was then that the Family reached its zenith, and 

 in the still later Cretaceous rocks of Europe, as a flame burns 

 brightest near its end, so some species suddenly assumed relatively 

 gigantic proportions, and as suddenly became extinct. A few sur- 

 vived in America down to that much later period, the close of the 

 so-called Cretaceous series on that continent. Only two types lived 

 on to the present day and only one of these has ever since Cretaceous 

 times been represented in our area. 



Turrited Gasteropods, with wing-like expansion of the shell, first 

 appear in the Middle and Upper Lias in France, but have not been 

 found in England in any rocks older than the Jurassic. Several 

 species were figured from the latter by Mr. W. H. Hudleston, F.R.S.,^ 

 showing how remarkably little modification some types reappearing 

 in the Cretaceous had undergone, and carrying our knowledge of the 

 British species back a very considerable stage. We thus see that 

 with the exception of the patelliform, heliciform, and trochiform 

 groups, the present is the most venerable for its antiquity. The 

 present paper will go far towards completing our knowledge of the 

 life-history of the Family in British strata, for in post-Eocene rocks 

 only slight modifications of the still existing species are met with. 



The Eocene group is composed of forms differing so slightly from 

 each other, that were the assemblage an existing one, we should 

 hardly hesitate to regard them all as coming well within the range of 

 variation of a single species. All belong to an ancestral type of the 

 living A. pes-pelecani, and thus to the true genus Aporrha'is. For 

 all biological purposes this statement might suffice, but in dealing 

 with fossils, other points have to be considered. They must be 

 so described that the general tendency and direction of the successive 



1 See Geol. Mag. Dec. II. Vol. VII. 1880, PI. XVII. Fig. 6, p. 632, and ibid., 

 Dec. III. Vol. L 1884, PI. VI. pp. 145-154, and PI. VII. pp. 193-200. 



DECADE III. VOL. I. — NO. XII. 34 



