206 PLIOCENE MOLLUSCA. 



Pleurotoma Selysii, De Koninck. Plate XXVI, figs. 17, 18. 



1837. Pleurotoma Selysii, De Koninck, Coq. foss. Basele, p. 25, pi. i, fig. 4. 



1843. Pleurotoma Selysii, Nyst, Coq. foss. Terr. Tert. Belg., p. 515, pi. xl, figs. 11", 12. 



1861. Pleurotoma Selysii, F. E. Edwards, Mon. Moll. Eoc. Form. Engl., pt. i (Palseont. Soc), 



p. 278, pi. xxix, fig. 17. 



1867. Pleurotoma Selysii, Speyer, Palaeontographica, vol. xvi, p. 189, pi. xx, figs. 1 — 5. 



1907. Pleurotoma Selysi, Eavn, K. Danske Vid. Selsk. Skrift. [7], vol. iii, p. 344, pi. vii, figs. 9—13. 



1913. Pleurotoma Selysi, Harder, Danm. Geol. unders^gelse [2], vol. xxii, p. 89, pi. viii, figs. 1 — 24. 



Specific Characters. — Shell slender, fusiform, turreted ; spire acuminate ; whorls 

 slightly convex below, excavated above, obscurely angulate ; ornamented by 

 exceedingly fine and close-set spiral lines, somewhat stronger toward the base of 

 the shell, hj a raised band with pliciform tubercles above the suture, and by fine 

 flexuous lines of growth, the last whorl being contracted and produced into a long, 

 straight and narrow canal ; mouth ovato-elongate ; the labial sinus, situated on 

 the shoulder, is wide and triangular. 



Dimensions. — L. 35 — 70 mm. B. 10 — 20 mm. 



Di.^tributiou. — Not known living. 



Fossil : Waltonian Crag : Little Oakley (derivative). Oligocene : 

 Holland, Belgium, Denmark, North Germany. Eocene : North London. 



BemarJiS. — The Crag specimen here figured is from Oakley, where it is no 

 doubt derivative. Although worn, it retains sufficient of its original sculpture to 

 be identified, in Mr. van der Gracht's opinion, with an Oligocene species, a specimen 

 of which, from one of the Dutch borings under his charge at Siepe, near 

 Winterswyk, he has been kind enough to send to me for comparison. 



P. Selysii was reported by F. E. Edwards from the Eocene deposits of 

 Hampstead, Finchley and elsewhere, but our fossil resembles more nearly the 

 Oligocene and Dutch variety of this species than the latter. 



Among the specimens of the Pleurotomidge from Oakley that I regard as deriva- 

 tive, there are a few others which, though clearly different from anything hitherto 

 reported from the Crag, are too imperfect for satisfactory reference. Some of 

 these M. van der Gracht thinks may belong to species from the Oligocene or 

 Miocene of northern Europe. It is to those deposits of the North Sea basin that 

 we may look, perhaps, with most prospect of success for the identification of such 

 derivative fossils. 



It is clear that a number of characteristic Miocene species were still living in 

 the Anglo-Belgian basin in Waltonian times, but it seems improbable that any 

 Oligocene forms like the present shell could have survived until that period. 



Nyst and De Koninck have reported P. Selysii from the Oligocene of Belgium, 

 Speyer from that of North Germany, and, more lately, Drs. Ravn and Harder 



