NERIN^A. 213 



also shorter. There is also some difference in details of ornament, but the differ- 

 ence of mineralization may partly account for this. It is a good local variety, if 

 not entitled to be regarded as a distinct species. 



Rare in the Lincolnshire Limestone at Santon, but more common at Geddington 

 G-range, where the specimens are usually weathered. 



Section E. — Folds numerous, simple. 



149. Nerin^a (? Ptygmatis) GuiSEr, Witcliell, 1880. Plate XV, figs. 1 a—c. 



1880. NEEiNiEA. GtriSEi, Witchell. Notes on a Section of Stroud Hill, &e., Proc. 



Cottesw.Nat. Field Club, vol. for 1879-80, 

 p. 128, pi. iv, fig. 2. 



1887- _ _ — Proc. cit., vol. for 1887, p. 25. 



Bibliography, ^c. — In the original diagnosis Mr. Witchell says, " Columella 

 with one fold, outer wall with two folds near the middle of the volution." Subse- 

 quently, having obtained better specimens, he described the species as possessing 

 " two folds on the columella, two on the outer wall, and one on the posterior wall.^' 



Description : 



Spiral angle (regular) . . . 3^°. 



Height of whorl to width about . . .1:1. 



Approximate length . . . .150 mm. 



Shell cylindrical, turrited. Whorls numerous, much excavated, and orna- 

 mented with closely-set fine spiral lines (rarely preserved, and probably not 

 extending to the more mature whorls). The constriction of the whorls is slightly 

 anterior, so that each sweeps up very sharply towards the raised anterior margin. 

 Sutural girdles extremely prominent, sutural angle very oblique. 



Aperture oblong, form and length of canal unknown. Section, five folds, with 

 two wide but simple folds on the outer walls, two smaller V-shaped folds on the 

 columella, and one small V-shaped fold on the posterior wall. 



Relations and Distribution. — This singular and well-marked species appears to 

 stand alone in the Inferior Oolite, and to be without near relations in any English 

 beds. It is somewhat difficult to say whether it should be regarded as a Nerinaea 

 or a Ptygmatis. The folds on the columellar side are small, so that the section is 

 not deeply indented. The existence of species having the internal structure of 

 Nerinaea cingenda and Nerinaea Guisei affords evidence of a bridge, as it were, 

 between the triplicate Nerinaeae and the more complex internal structure of 

 Ptygmatis. 



