456 PLTOCENE MOLLUSCA. 



beyond those below them ; suture slight but channelled ; ornamented b}' two 

 flattened spiral ridges, plicate rather than carinate, the lower one rather the more 

 prominent, and by exceedingly fine spiral lines. 



Dimensions. — L. 45 — 50 mm. B. 12 — 14mm. 



Distribution. — Not known living. 



Fossil : Waltonian Crag : Little Oakley. 



Lower Pliocene (Piacenziano) : northern Italy. 



Upper Pliocene (Astigiano) : Monte Mario. 



Remarks. — The fossils represented under the above name, of which I have 

 obtained several examples from Oakley, correspond very closely with those figured 

 by Sign. Cerulli-Irelli from Monte Mario, where he says they are not rare. They 

 seem to separate themselves by their special spiral sculpture from the rest of the 

 many Turritellas I have obtained from Oakley, most of which may be referred to 

 T. (Haustator) triplicata or T. (Haustator) iucrassata, forms which, as stated above, 

 I regard as specifically distinct. They differ from the Miocene shell T. bicarinata, 

 described below, in that their spiral- ridges are flattened, the lower one being the 

 more prominent, besides which the latter species is regarded by Prof. Sacco and 

 M. Cossmann as belonging to a different sub-genus, Archimediella. 



The specimen from the Scaldisien of Antwerp figured by Nyst in 1881 as 

 T. iucrassata, var. bicincta (op. cit.), may be probably the present form. The var. 

 y, bicincta of Wood (Mon. Crag Moll., pt. i, pi. ix, fig. 7 d, 1848) is a different 

 shell (see p. 439 of the present work). 



It may be again noticed that many specimens of the Crag Turritellas which we 

 have been accustomed to regard as varieties of T. iucrassata, seem rather to group 

 themselves Avith certain Pliocene or Miocene forms which continental Conchologists 

 have regarded as specifically or even as sub-generically distinct. 



Sub-genus ARCHIMEDIELLA, Sacco, 1895. 

 Turritella (Archimediella) bicarinata (Eichwald). Plate XLIII, figs. 19, 20. 



1830. Turritella bicarinata, Eichwald, Naturhist Skizze v. Litbauen u. Volhynien, p. 220. 



1856. Turritella bicarinata, Homes, Foss. Moll. Tert, Wien, vol. i, p. 426, pi. xliii, figs. 8—12 



1876. Turritella bicarinata, Seguenza, Boll. R. Com. Geol. Ital., vol. vii, p. 100, no. 638. 



1882. Turritella Archimedis, von Koenen, Nord-deutsch. Miociin Moll. -fauna, vol. ii, p. 285, no. 190. 



1886. Turritella bicarinata, Dollfus et Dautzenberg, Feuilles des jeunes Nat., vol. xvi, p. 138. 



1889-95. Turritella bicarinata and vars., Sacco, Boll. Soc. Greol. Ital., vol. viii, p. 352, no. 1890, 1889 ; 



Archimediella bicarinata and vars., Moll. Terr. Terz. Piem., pt. xix, p. 14, pi. i, figs. 48 — 52, 1895. 

 1903. Turritella bicarinata, Dollfus, Cotter et Gomes, Moll. Tert, Portugal, p. 4, pi. xxx, fig. 4. 

 1907. Turritella Archimedis, Ravn, Kongl. Danske Vid. Selsk. Skrift., vol. vii, p. 296, pi. iii, fig. 15. 

 1912. Turritella (Archimediella) bicarinata, Cossmann, Ess. Pak'oconcb. compar., vol. ix, p. 122, 



pi. vi, figs. 29, 30. 



