670 PLIOCENE MOLLUSCA. 



Genus CITHNA, A. Adams, 1863. 

 Cithna minima, A. Bell, MS. Plate LIII, fig. 33. 



1892. Cithna minima, A. Bell, Eep. Yorks Phil. Soc, p. 75. 



Specific Characters. — Shell minute, oval, conical ; whorls 4, the last angulated, 

 comprising nearly the whole length ; upper whorls and apex depressed, suture 

 well marked; mouth nearly circular with an expanded base; inner lip curved; 

 basal chink long and narrow. 



Dimensions. — L. 1 mm. B. 1 mm. 



Distribution. — Not known living. 

 Fossil : Selsey. 



Remarks. — The minute shell here given has been identified by Mr. Bell as the 

 one found at Selsey and described by him under the above name. It now belongs 

 to the Museum at York where it has been labelled Cithna depressa. At present 

 it is unique, not having been recorded, so far as I know, by any other observer, or 

 from any other locality. 



Cithna incerta, A. Bell, MS. Plate LIII, fig. 34. 



Specific Characters. — Shell minute, smooth, turreted ; whorls 4, convex, the last 

 ventricose, much the largest; suture deep; spire regularly diminishing in size 

 towards a rounded and compressed apex ; mouth ovate, angulate above ; peristome 

 continuous ; umbilicus large, open. 



Dimensions. — L. 2 mm. B. 1 mm. 



Distribution. — Not recorded living. 

 Fossil : St. Erth. 



Remarks. — The charming little shell figured under this name was found by 

 Mr. Bell at St. Erth, and is now in the Warburton Collection at the British 

 Museum (Nat. Hist.). It has not been recorded hitherto as a fossil from either 

 any British or continental deposit. 



Cithna has been regarded by P. Fischer as a sub-genus of Lacuna, to which 

 it seems nearly allied, but Carus and the authors of the ' Marine Mollusca of 

 Roussillon ' consider it a distinct genus. A Mediterranean shell, C. tenella (Hela, 

 Jeffreys) has been taken to represent the type. 



Genus FOSSARUS, Philippi, 1841. 



Fossarus sulcatus (S. V. Wood). Plate LIII, tig. 35. 



1842 — 50. Phasionema sulcata, S. V. Wood, Ami. Mag. Nat. Hist. [1], vol. i\, p. 535, Is 12 ; Fossarus 

 sulcatus, Mon. Crag Moll., pt. i, p. 121, pi. viii. figs. 23 a, 23?;, 1848 ; pt. ii. p. 317, 1850. 



