GASTEROPODA. 33 
NV. Testa turrito-conicd, spird angulo 18°—22°, anfractibus subplanis inornatis ; colu- 
mella crassd, prius solidd denique perforatd, plicas duas parvas, remotas gerente; labro 
dextro intus uniplicato, apertura rhomboidali. 
Shell elongated, conical, smooth; in its young state there is usually a slight depression 
round the lower part of each whorl, this is gradually lost in the larger whorls, which are 
quite flat ; but specimens may be found in which all the whorls are slightly convex. The 
columella is solid in the young shell; but usually becomes perforated about an inch below 
the apex ; there is great variety in this respect in different specimens, the perforation some- 
times commencing within half an inch from the apex, while other shells, an inch and a half 
long, may be found quite solid. The spiral angle also varies from 20° to 22° in different 
specimens ; in some instances the sides of the shell are straight, in others the lower part is 
more cylindrical than the upper; in some few instances the lower part of the shell enlarges 
more rapidly than the upper, in which case the perforation of the columella is unusually 
large. Thus the species varies in its external form, from a neat, regular shell to a 
very clumsy one. ‘The aperture is rhomboidal, its height being half as much again as its 
width, ending below in a short canal. There are three internal folds, viz.: one on the outer 
lip, near to the base of the whorl, which is insignificant at the aperture, but long and strong 
in the imner whorls; another, thick and blunt on the columella, a little below the preceding; 
thirdly, one small and blunt on the top of the whorl. These folds are very constant in 
form, and serve to distinguish the species readily. 
Siiuraleanolet.) savy ws) fo pcs) eee (ee TOMO. 
Basal angler. ivy iy pany: Mian es shone ton o On 
Length, 1 inch to 23 inches. 
‘In the young state, or when the axis does not exceed 10 or 12 lines, the aspect is so 
dissimilar of this protean shell, that a particular description of that condition is necessary :— 
It is taper and pointed, the volutions are convex, very narrow, an individual of 9 lines 
having as many whorls. The sutures are very deeply depressed, the shell is altogether 
delicate and fragile, but perfectly regular. Specimens exceeding 10 lines increase dispro- 
portionally in the height of their whorls ; they become more flattened, the sutures are less 
strongly defined, the shell acquires a considerable increase of thickness, and the whole is 
changed. 
Locality. This specimen occurs in every stage of growth and throughout the entire 
thickness of the formation in Gloucestershire; its habits were gregareous—the shelly 
weatherstones more especially contain it in great numbers. 
Nerin#A (Trocnatia) Evprsi. Plate VII, fig. 6, 6a. 
? CerttHium Derrancii, Deslongehamps. Mém. Soc. Linn. Normandie, vol. vii, pl. 8, 
fig. 36. 
N. Testé turritd, conicd, anfractibus (10) concavis, angustatis, liners transversis cinctis 
