264 
GASTEROPODA OF THE INFERIOR OOLITE. 
Numerous lines of growth decussate with very fine spiral lines ; and some 
specimens exhibit a spiral punctate structure. This is especially the case with 
specimens from the Humphriesiamis -zone of North Dorset, where a fine reticulate 
structure scarcely interferes with the general smoothness of the shell.^ 
Relations and Distribution. — Although the form of this little shell is Euspiroid 
it is by no means clear that Lycett would have placed it under Euspira, because 
of the narrowness of the sutural ledge. Fig. 13 u may be taken as nearly an 
average specimen, inclining to be rather wide ; whilst 13 & represents an excep- 
tionally narrow variety, somewhat approaching N. Calypso, d’Orb. 
This species is extremely abundant in the Parkin soni-zone of South Dorset, 
especially at Burton Bradstock. It also occurs in the upper part of the 
Humpliriesianus-zone of North Dorset, and notably in the G ad omensis -bed at 
Oborne. These specimens are for the most part wider-angled, the narrowest 
specimens coming from the upper part of the Farkmsoni-zone. N. Bajocensis 
occurs in the Parkins oni-zone of Bradford Abbas, at Lodge Hill near Castle Cary, 
and at some other places, though not abundantly. But it may be always expected at 
the confines of the Humphriesianus and Parkinsoni-zones. A few typical specimens 
may be collected at Aston and Notgrove. 
In the Cotteswolds N. Bajocensis appears to be partially replaced by a form 
nearly twice the size, but not dissimilar in proportions. It generally occurs in 
an imperfect condition. This is probably the form referred by Mr. Witchell to 
Natica Strickland.i, Mor. and Lyc. See remarks on No. 196.^ 
N.B. — Natica punctura. Bean {pars). See Plate XX, fig. 14. ' 
Littoeina punctttea, Bean. Magazine of J^atural History, vol. iii, p. 62, fig. 23. | 
Natica punctuea, Bean. Hudleston, Geol. Mag., dec. 2, vol. ix, p. 201, pi. v, ' 
fig. 10. 
Shells from the Dogger thus referred exhibit a spiral angle of about 65° ; ratio : 
of the body-whorl to the full length 60 : 100, usual length 25 mm. The whorls I 
are scarcely in steps, the sutural ledge being very narrow ; the body-whorl is rather ' 
more tumid than in N. Bajocensis. Specimens from the Dogger are full size, and | 
often spirally punctate (condition). Specimens from the Scarborough Limestone, | 
when well preserved, show a fine linear spiral structure. They are usually shorter I 
^ As this peculiar brown translucent calcite shows up the structure very well in other fossils we I 
may presume that much depends upon the character of the mineraliser. i 
2 Antea, p. 261. j 
