634 PLIOCENE MOLLUSCA. 



The fossil here represented is from the British Museum of Natural Historj^, where 

 it bears the above name. It is worn and shows but little indication of what the 

 scul})ture may have been, but in form coi'responds fairlv well with the figures 

 in some of our text-books. I accept, provisionall}- aud with some doubt, the 

 British Museum identification of our si)ecimeu in the hope that a more satisfactory 

 one may turn up hereafter. 



Rissoa seniicostata (S. Woodward). Plate LI, figs. 16, 17. 



1833. Turbo semicostatus, S. "Woodward, G-eol. of Norfolk, p. 44, pi. iii. fi^. 19. 



1842—72. Rissoa seniicostata, S. V. Wood, Ann. Mag. Nat. Hist. [1], vol. ix, p. 533, 1842 ; Mon. 



Crag Moll., pt. i, p. 102, pi. xi, fig. 10 ; B. pnlckella (not Phil.), p. 104, pi. xi, fig. 9 ; 



B. curficosfata, pt. i, p. 102, 1848 ; B. semicostata, 1st Suppl., pt. i, p. 72, 1872. 

 1864. Bissoa hiconspiciia, S. P. Woodward in White's Hist, of Noifolk, ed. 3, p. 118. 



1871. Bissoa cnrticosfata, Jeffreys iti Prestwich, Quart. Jouru. Gteol Soc, vol. xxvii, p. 4i»0 (not 

 B.2)ulcheUa,V\n\.). 



1872. Bissoa curticostata, A. and E. Bell, Proc. G-eol. Assoc, vol. ii, jap. 210, 214. 

 1879. Rissoa curticostata, J. Reeve, Trans. Norwich Geol. Soc, vol. i, p. 70. 

 1890. Rissoa curticostata, C. Reid, Plioc. Dep. Brit., p. 255. 



1912. Bissoa semicostata, Tesch, Med. v. d. Rijks. v. Delfstoffen, No. 4, p. 68, no. 154. 



Specific Gliaracters. — Shell small, ovato-conical ; wliorls 5 or 6, convex, the 

 last tumid, much the largest; ornamented by about 20 longitudinal costa?, not 

 very prominent, which do not reach the base, and by inconspicuous spiral lines, 

 rather stronger, near the periphery ; spire short ; suture fairly deep ; month 

 irregularly oval ; outer lip thickened, denticulated within. 



Dimensions. — L. 4 — 5 mm. B. 2'5 — o mm. 



Distrihutiou. — Not known living. 



Fossil : Waltonian Crag : Walton-on-Naze, Little Oakley. New- 

 bournian : Sutton, Kesgrave, Bentley. Butleyan : Butley. Icenian : Bramerton, 

 Yarn Hill. Middle Glacial sands : Billockby. 



Remarks. — This little shell may be found at a nundjcr of localities in the East 

 Anglian deposits, and especially in the more recent part of the Red Crag at Butley 

 and in the Icenian of Bramerton ; at both of these horizons it is faii'ly abundant. 

 I figure a specimen from each which may be taken as more or less typical. The 

 sculpture varies considerably from that shown in my fig. 1 7 from Butley to that 

 of fig. 16 from Bramerton, in Avhich the costse are less distinct and more numerous. 

 Other varieties occur occasionally in which the ribs are nearly and sometimes quite 

 obsolete. It was first noticed in 1833 by Samuel AVoodward, of Norwich, who 

 identified it with the Tnrho semicostatus of Montagu; the correctness of this view 

 Wood doubted, proposing to call it U. cnrticostata, in which he was followed 

 by Jeffreys, the l:)rothers Bell and C. Reid. Haviug found, however, that the 



