NERINiEA. 197 



to be distinguished from this species are of occasional occurrence. Figs. 15 and 

 16, representing specimens from Weldon, might possibly be referred to as 

 immature forms. 



122. Nerintea {Nerinella) conoidea, sp. nov. Plate XII, fig. 14. 

 (But see Witchell, vol. cit., p. 37, pi. ii, fig. 1.) 



Description : 



Spiral angle (slightly obtuse) . . .12° 



Height of whorl to width . . . 1 : 1*25 



Approximate length . . . .80 mm. 



Shell cylindro-conical, apical whorls alone turrited. The whorls are about 

 twenty in number, increasing by slight steps in the earlier stages, where, also, 

 each whorl has a slight posterior prominence ; the matured whorls are without 

 any prominence in the neighbourhood of the sutures, and perfectly flat. No 

 specimens showing apical ornaments have as yet been found. 



Aperture as in the preceding species but less elongate ; internal section similar. 



Relations and Bistrihution. — If we are to allow that the differences in these 

 very plain Nerinellse justify us in making specific distinctions, it is chiefly in the 

 relative proportions of the spiral angle and the whorls that we must look for the 

 evidences. The difference between such shells as figs. 12 and 14, one having a 

 spiral angle of 5° and the other of 12°, is most striking, and almost forbids us to 

 include them under the same species. 



Occurs on the Oolite Marl horizon, chiefly at Swift's Hill and Longridge. 



123 — 126. Species of uniplicate Nerinella found in the Lincolnshire Limestone at 



Weldon. Plate XII, figs. 15—18. 



A 1 (fig. 15). Spiral angle 8°, height of whorl to width 1 : 1-25, length of 

 figured specimen 11 mm. Shell elongate and not turrited ; whorls smooth ; 

 aperture oblong with a well-marked canal. Section uniplicate. 



A 2 (fig. 16). Spiral angle 12°, height of whorl to width 1 : 1-35, length of 

 figured specimen 18 mm. Shell elongate and slightly turrited; whorls smooth. 

 Body- whorl somewhat constricted ; aperture and section as in the preceding. 

 These two forms might almost be taken to represent the early stages of N. gracilis 

 and N. conoidea respectively. 



