696 PLIOCENE MOLLUSCA. 



from the Warburton Collection at the British Museum which is there considered to 

 be a new and distinct species under the MS. name of X. approximate Etheridge 

 and Bell. 



Natica (Lunatia) assimilis, sp. nov. Plate LIV, fig. 17. 



Specific Characters. — Shell solid, ovate ; whorls 5, the last much the largest, 

 occupying nearly the whole length ; spire very short, rapidly diminishing in size 

 to a blunt and depressed point ; lines of growth very fine, indistinct ; suture well 

 marked ; mouth semilunar, large ; angulate above, rounded below, somewhat 

 expanded ; umbilicus open, rather large. 



Dimensions. — L. 29 mm. B. 24 mm. 



Distribution. — Not known living. 

 Fossii : St. Erth. 



Remarks. — The specimen figured under this name from St. Erth belongs to the 

 Warburton Collection at the British Museum, where it is labelled X. variant, Duj. 

 For reasons given above I think this is a mistake, neither can it be referred, 

 I consider, to the shell I have called N. exvarians, the mouth of which is smaller 

 and the spire longer and more prominent. It comes nearer to N. helicina, 

 especially to the pro-helicina of Prof. Sacco, but it is larger and on the whole, I 

 think, deserves a distinguishing name. The St. Erth Naticas seem a distinct 

 group, having no actual affinity to those of any other horizon of the British 

 Pliocene, most of the forms that have come under notice and are here figured 

 having a short and depressed spire. 



Natica (Lunatia) varians (Dujardin, rum Wood). Plate LIV, fig. 14. 



1837. Natica varians, Dujardin, Bull. Soc. gc'ol. France, vol. ii, p. 281, pi. xix, fig. 6. 



1874. Natica hemiclausa (N. varians, Duj.), Van den Broeck, Ann. Soc. malac. Belg., vol. ix, pp. 



134, 187. 

 1886. Natica (Naticina) varians (Duj. non Wood), Dollfus et Dautzenberg, Feuille des Jeunes 



Natur., vol. xvi, p. 141. 

 1890—91. Natica catena var. variaris, Sacco, Boll. Soc. G-eol. Ital.. vol. ix, p. 311, no. 5017, 1890; 



Moll. Terr. Terz. Piem., pt. viii, p. 69, pi. ii, fig. 41, 1891. 



Specific Characters. — Shell rather small and slender ; oval, subcorneal ; whorls 

 5, but slightly convex, the last much the largest, four-fifths the total length ; 

 spire very short, compressed, with a blunted point ; suture slight ; mouth large, 

 acutely angulate above, rounded below; outer lip incurved; inner lip straight, 

 thickened above by a callus which nearly covers the umbilicus. 



Dimensions.— L. 20 mm. B. 16 mm. 



Distribution.— Not known living-. 



O 



Fossil : Miocene: Belgium, Touraine, Bordeaux, Piedmont. 



