208 PLIOCENE MOLLUSCA. 



some extent, the moutli and outer lip are different; it is now referred to the 

 genns Ti/pltlomaiKjilia of M. Sars. I doubt, as "Wood did, Avhether the Miocene 

 fossil and the Recent shell are the same. 



Siih-genm HEMIPLEUROTOMA, Cossmann, 1889. 

 Pleurotoma (Hemipleurotoma) denticulata (Basterot). Plate XXA^I, figs. 7, 8. 



1825. Pleurotoma denticula, Basterot, Descript. Coq. foss. Bordeaux, p. 63, pi. iii, tig. 12. 



1832. Pleurotoma denticula, Grateloup, Tab. Coq. Dax, p. 320. 



1843. Pleurotoma denticula, Nvst, Coq. foss. Terr. Tert. Belg., p. 526, pi. xliv, fig. 2. 



1847. Pleurotoma denticula, Bellardi, Mem. R. Accad. Sci. Torino [2], vol. ix, p. 576, pi. iii, fig. 7. 



1877. Pleurotoma denticula, Bellardi, Moll. Terr. Terz. Piem., pt ii, p 27, pi. i, fig. 17. 



1886. Pleurotoma denticulata, Dollfus et Daiitzenbei'g, Et. prel. Coq. foss. Toui-aine, p. 9. 



1896. Hemipleu7'otoma denticula, Cossmann, Ess. Palcoconch. comp., vol. ii, p. 78, pi. v, figs. 9, 10. 



Specific Characters. — Shell elongato-fusiform, turreted ; whorls 8, carinated 

 the upper part concave, finely striated ; the last rather more than half the total 

 length, excavated below, the base spirally ridged ; ornamented by a single row of 

 prominent tubercles on the keel ; apex blunt ; suture deep and channelled ; mouth 

 oval, angulated by the keel, with an angulated notch above ; canal rather short 

 and narrow, turning slightly to the left. 



Dimensions. — L. 15 — 25 mm. B. 6 — 10 mm, 



Disfri'hiit/oii. — Not known living. 



Fossil : Coralline Crag : Gedgrave, Waltonian : Little Oakley. 

 Miocene : Belgium, France, Italy. 



Remarks. — Hemipleurotoma, of which the Miocene P. deiiticuhi of Basterot is 

 taken as the type, has been proposed by M. Cossmann as a sub-genus for a group 

 of Pleurotomas with a short and nearly straight canal. I have obtained one 

 perfect specimen and a few recognizable fragments of the present species from 

 Oakley, and there is another, immature, from the Coralline Crag, in the Sedgwick 

 Museum, Cambridge. They correspond with a shell I brought some years ago 

 from the Miocene deposits of Saubriguez near Dax in south-western France, 

 which I have figured with my Oakley fossil to show their close resemblance. 

 The latter has no appearance of being derivative. I regard it as another of the 

 characteristic Miocene species which lingered on in the Anglo-Belgian basin 

 until the earliest part of the Red Crag period. 



The present form is not unlike a shell from the North German Miocene 

 described by Prof, von Koenen as P. Hosiusi, of Avhich he has kindly sent me a 

 specimen, but it differs from the latter in size and in its coarser sculpture. 



