308 PLIOCENE MOLLUSCA. 



Specific Characters. — Shell turreted, elongate ; whorls 6 — 8, convex, regularly 

 diminishing in size to a blunt and rounded apex ; ornamented by fine, closely-set 

 spiral ridges which extend to the base of the shell ; spire elevated, varying much 

 in its comparative length ; suture well-marked but generally not very deep ; mouth 

 long, sub-trapezoidal, angulate above ; outer lip compressed in the middle, nearly 

 straight, thickened and toothed internally ; canal wide, open, very short, turning to 

 the left ; columella flexuous, excavated. 



Dimensions. — (Very variable) L. 15 — 30 mm. B. 8 — 12 mm. 



Distribution. — Not known living. 



Fossil: Coralline Crag: Gedgrave, Sutton, Boy ton. Waltonian: 

 Walton-on-Naze, Beaumont, Little Oakley. Newbournian : Waldringfield, Ranis- 

 holt, Felixstow, Sutton, Bentley. Butleyan : Butley, Holleslcv. 



Middle Glacial sands : Billockby. 



Scaldisien : Belgium, Dutch borings. 



Remarks. — The present species, so far as I know, has been recorded as fossil from 

 the Anglo-Belgian region only, and is apparently an extinct form. It is one of 

 the common and characteristic species of the Waltonian deposits, but it is not so 

 abundant either in the Coralline or the later horizons of the Red Crag. It varies 

 considerably, especially in the length of the spire. Sowerby figured two forms, 

 Wood's varieties n and /3 ; the first (var. elongata) a slender shell with an elongated 

 spire, convex whorls, and a deep suture; the other with a shorter spire and flatter 

 whorls. For the latter Mr. A. Bell proposed in 1871 (op. cit.) the specific name 

 abbreviata, remarking that " the long and short varieties are constant and easily 

 distinguishable, even in immature specimens." My experience with the Oakley 

 fossils is somewhat similar, but the short-spired shells found at that locality are 

 not all abbreviated, ranging in length from 15 to 30 mm. or more. 



The Crag G. (Mitrella) sulcata is allied to the C. (Mitrella) erythrostoma of the 

 Italian Pliocene, but it is always spirally striated, the whorls are more convex, 

 and the suture is deeper. Specimens of the Crag shell which have lost their outer 

 coating have sometimes been mistaken for the Italian species. 



Columbella (Mitrella) sulculata (S. V. Wood). Plate XXXIII, tigs. 18, 19. 



1879. Columbella (Astyris) sulculata, S. V. Wood, Mori. Crag Moll., 2nd Suppl., p. 4, pi. i, fig. 3. 



1890. Columbella sulculata, C. Reid, Plioc. Dep. Brit., p. 243. 



1901. Anachis sulculata, Cossmann, Ess. Palcoconcb. comp:ir., vol. iv, p. 238. 



1915. Columbella sulculata, A. Bell, G-eol. Mag. [6], vol. ii, p. 167. 



Specific Characters. — Shell solid, slender, turreted, elongate, smaller than the 

 last species ; whorls 6 or 7, but slightly convex, regularly diminishing in size to a 

 blunt point ; spire elevated, of variable length ; suture well marked but not deep ; 

 ornamented with clearly-cut and closely-set spiral ridges which reach to the base 



