NERIN AA. 911 
Height of whorl to width (mean about) des; 
Approximate length : - 100—140 mm. 
Shell subeylindrical, turrited. _Whorls numerous, and variable in relative 
proportions, but on the whole rather high. At first the sutural belt or carina is 
very prominent, ahd the whorl very concave (13 5). Presently the whorls are 
divided almost equally by a median belt, the anterior portion being excavated 
whilst the posterior portion is flat. Fine spiral lines with faint granulations are 
usually present, but appear to fail in the anterior whorls, where a considerable 
modification takes place, though, on the whole, the somewhat long whorl, the 
median varix, and the constricted anterior area are usually characteristic. 
Available specimens rarely have a good aperture, and the actual body-whorl is 
seldom seen. Fig. 13 a shows a good aperture, with one wide fold rather below 
the centre of the outer wall, and two finer folds on the columella. It is 
probable, however, that this is not the real body-whorl, but merely the lowest 
whorl of an imperfect specimen.’ The very small posterior fold on the outer 
wall may not have been developed in this particular case. The section is shown in 
figs. 13 d and 13 e, both from the Dogger of Blue Wyke. It may be described as 
triplicate to quadruplicate. The posterior fold on the outer wall is small, and not 
always present in every whorl of the same specimen. Fig. 14 represents a cast 
of a fragment of a large specimen from the ironstone of Irchester, where the 
posterior fold of the outer wall has been developed on one whorl and not on 
another. 
Relations and Distribution—In Yorkshire Nerinza cingenda occurs abundantly 
in the upper part of the shell-bed towards the top of the Dogger at Blue Wyke, 
but has never yet been found in any part of the Dogger below that bed. It may 
also occur in the Millepore Bed, though I have not been able to identify it 
for certain.” From its proneness to dimorphism, and the variability of its internal 
section, it affords an excellent example of the instability of the genus, of which in 
Yorkshire it is the first representative. The two species, or sub-species, next 
described are its more immediate relatives. 
As regards distribution in other parts of England, N. cingenda may usually be 
looked for on the Dogger-horizon in the counties of Lincoln, Rutland, and 
Northampton, although I only know of it myself in the last county. Many of 
the large casts in the Duston ironstone belong to this species. As we proceed 
south-westwards there seems to be an indication of it in the Inferior Oolite of 
Otley Hill. I have never seen genuine specimens from the Cotteswolds, although 
1 See antea, p. 195. 
2 Although I possess several interesting fragments from the Millepore-bed, one of which is a 
Ptygmatis, they are too imperfectly preserved for description. In the Scarborough Limestone, as is 
usual where a Cephalopod facies predominates, Nerinea is hardly to be found. 
