NERIN.EA. 215 



151. Neein^a (Ptygmatis) pisolitiuAj Witchell, 1887. Plate XV, figs. 3 a — c, and 



Plate XVI, fig. 7. 



1887. Nebik^a pisolitioa, Witchell. Vol. cit., p. 32, pi. i, fig. 6. 



Description : 



Spiral angle .... 3° — 5°. 



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



Approximate length . . . 80 — 200 mm. 



Shell cylindrical, subulate. Whorls numerous, of moderate length, flat, 

 sutural prominence scarcely marked. Assuming that fig. 3 h represents the apical 

 conditions, there are numerous fine spiral lines in the earlier whorls, whilst the 

 later ones appear to have been perfectly smooth. 



In section the outer wall has two folds, the anterior of which is very large and 

 complex ; the posterior fold is small and flat-headed. On the columellar side the 

 anterior fold is expanded and angulated, the middle fold is almost simple, the 

 posterior fold is deep and bifurcated. 



Relations and Distribution. — The internal structure easily distinguishes this 

 species from any member of the Oppelensis-gvouj), where the section exhibits seven 

 folds ; the whorls also are perfectly flat throughout, whilst inmost of the members 

 of the Oppele7isis-grou-p they are excavated, at least in the earlier stages. 



It is described by Mr. Witchell as abundant in tlie pisolitic beds near Stroud, 

 and at Longfords near Nails worth. It occurs also in the Pea-grit at Crickley. 

 There is a variety with rather shorter whorls, a rather wider spiral angle, and 

 with the apical whorls slightly excavated, which occurs in a hard arenaceous rock 

 about halfway between Seven Wells and Snow's Hill. This is said tu be on the 

 horizon of the Oolite Marl. Very long specimens showing the characteristic 

 internal structure of Ptyg. pisolitica occur in the Inferior Oolite of Otley Hill (Mr. 

 Walford's collection.) The fragment from Weldon (PI. XVI, fig. 7) also greatly 

 resembles this species, which, if this identification be correct, appears to possess a 

 wide vertical range. The shell-bed at Weldon is undoubtedly high^ in the Inferior 

 Oolite series, but there is probably a mixture due to remanio forms. 



^ When I spoke of the Lincolnshire Limestone as being in the Lower Division of the Inferior 

 Oolite ;in exception should have been made as regards the fossiliferous beds of Weldon and Great 

 Ponton (see antea, p. 73). 



