698 PLIOCENE MOLLUSCA. 



Fischer, however, whom as a rule T follow, adopts that name as a sub-genus of 

 Natica, which he says is an oval elongate shell, having the umbilicus wholly or 

 nearly closed by the funicular callosity. 



Natica (Polinices) hemiclausa (J. Sowerby). Plate LVI, fig. 16. 



1825. Natica hemiclausa, J. Sowerby, Miu. Conch., vol. v, p. 125. pi. cccclxxix, fig. 2. 



1844. Natica macilenta, Philippi, Eimm. Moll. Sic, vol. ii, p. 140, pi. xxiv, fig. 14. 



1871. Natica hemiclausa, Jeffreys in Prestwieh, Quart. Journ. Geol. Soc, vol. xxvii, p. 489. 

 L872. Natica hemiclausa, A. Bell, Geol. Mag., vol. ix, p, 210. 



1872. Natica hem id ansa, A. and R. Bell, Proc. Geol. Assoc, vol. ii, pp. 209, 213, 216. 



1873 — 6. Natica macilenta, Segueuza, Boll. R. Com. Geol. Ital., vol. iv, p. 352. no. 260. 1873 : vol. v, 



p. 280, no. 105, 1874 ; vol. vii, p. 10, no. 485, 1876. 

 1874 — 92. Natica hemiclausa, Van den Broeck, Ann. Soc malac Belg., vol. ix, p. 134, 1874; Bull. 



Soc Beige Geol., vol. vi (Memoires), p. 133, 1892. 

 1881. Natica hemiclausa, Nyst, Couch. Terr. tert. Belg., p. 71, pi. v, fig. 11. 

 1890. Natica hemiclausa, C. Reid, Plioc Dep. Brit., p. 249. 

 1890. Natica (Naticina) macilenta, Carus, Prod. Faun. Medit., vol. ii, p. 3l)5. 

 1901. Natica (Naticina) macilenta, Kobelt, Icon, schalentrag. europ. Meeresconch., vol. ii, p. 92, pi. Hi, 



figs. 13, 14. 



1912. Natica hemiclausa, Tescli, Med. v. d. Rijks. v. Delfstoffen, No. 4, p. 66, no. 145. 



1913. Natica macilenta, Gignoux, Ann. de l'Univ. de Lyons [n. s.], vol. xxxvi, p. 562. 



Specific Characters. — Shell strong, smooth, oblique, subglobose, generally 

 small ; whorls 5 or 6, overlapping, the last tumid, much the largest, about four- 

 fifths the total length; spire regularly conical, rapidly diminishing to an acute 

 apex ; suture very slight ; mouth large, semilunar, angulate above, rounded and 

 projecting below ; outer lip regularly curved, not expanded ; inner lip forming 

 a rather wide callus upon the columella, which nearly and sometimes entirely 

 covers the umbilicus. 



Dimensions. — L. 12 — 15 mm. B. 10 — 12 mm. 



Distribution. — Recent : As N. macilenta, Atlantic coasts of Spain. Mediter- 

 ranean, widely diffused. Adriatic. 



Fossil : Waltonian Crag : Walton-on-Naze, Beaumont, Little 

 Oakley. Newbournian, Butleyan : passim. Icenian (less abundant) : Aldeburgh, 

 Bulchamp, Southwold, Yarn Hill, Easton Bavent, Bramerton. Weybourne. 



Pliocene : Belgium, Holland, France, Italy. 



Pleistocene : Sicily, Calabria, Tuscany. 



Remarks. — IV. hemiclausa, a variable shell, very characteristic of the Red Crag, 

 and specially abundant in the Waltonian zone at Little Oakley, was original 1\ 

 described by Sowerby from a small specimen about lb' mm. high, which Wood was 

 disposed to regard as immature. I have found a hundred examples or more of a 

 similar form at Oakley. They are nearly all about the same size and appear to be 

 full-grown. The specimen figured by Wood in 1848 as A. hemiclausa 1 seems to me 



1 Mon. Crag Moll., pt. i, p. 144, pi. xvi, fig. 5. 



