196 GASTEROPODA OF THE INFERIOR OOLITE. 
fossils having been remani? from earlier beds destroyed by contemporaneous 
erosion. At Great Ponton only Nerinea has been noticed by me; the 
specimens are less fragmentary than at Weldon, but their surface condition is 
sadly apt to mislead. When to these difficulties we add the prevalence of dimor- 
phism, it must be allowed that the Nerinzeas of the upper beds of the Lincoln- 
shire Limestone (Weldon and Great Ponton) constitute about as undesirable 
a group as any one could have to investigate. One thing, I think, comes out 
pretty clearly, viz. a strong admixture of forms related to and nearly identical 
with those in Bathonian beds. 
Srotion A (UnipiicaTs). 
121. Nerina (Nerinella) cracttis, Lycett, 1857. Plate XII, figs. 12, 13 a, 13 b. 
1853. Curmnirzta Graciuis, Lycett. Proc. Cottesw. Nat. Field Club, vol. i, p. 79, 
pl. ii, fig. 3. 
1857. Nerinma aracriis, Lycett. Cotteswold Hills, p. 124, pl. 1i, fig. 3. 
1887. — — — Witchell, Proce. Cottesw. Nat. Field Club, vol. 
ix, p. 37, pl. ii, fig. 2. 
Description : 
Spiral angle : : ; . d—8°, 
Height of whorl to width . : fo PPPRAELS! 
Approximate length ; . 60—140 mm. 
Shell cylindrical, scarcely turrited. Whorls twenty-five or more, with a slight 
posterior prominence in the younger shells; flat or very slightly turrited in the 
more matured whorls. No sutural carina. Fine spiral lines mark the anterior 
portion of each whorl, of which the prominent portion is smooth. In the more 
advanced stage the whorls are smooth. 
Aperture ovate-oblong, with a narrow and but slightly twisted canal. Section 
uniplicate, with one simple fold in the middle of the outer wall. 
Relations and Distribution.—In order not to multiply specific names unduly a 
considerable breadth of variety as regards spiral angle has been admitted in this 
case. It is just possible that fig. 12 may represent a narrow variety, of which 
fragments representing very long shells are occasionally found. Lycett’s type 
was from the Oolite Marl horizon at Nailsworth Hill; the other specimens are 
from the Oolite Marl of Swift’s Hill or Longridge, where N. gracilis is moderately 
plentiful in fragments. In the Lincolnshire Limestone, specimens of Nerinella not 
1 In referring to the Oolite Marl the horizon is meant, see p. 61, antea. 
