228 
GASTEROPODA OE THE INFERIOR OOLITE. 
There can be no doubt whatever that the specimen from the Upper Lias of 
Heyford (PL XVII, fig. x), procured by Mr. Crick of Northampton, is closely 
related to M. euglypJia, Laube, though sufficiently different perhaps to be regarded 
as specifically distinct. The “ embryonic button ” and general features of the 
shell speak strongly in favour of its being placed under the genus Mathilda. 
Possibly most of the Turritellids figured on PI. XVII, with the exception, perhaps, 
of T. Dorsetensis, might be allowed to follow suit. As a matter of fact I propose 
to describe these species under the genus Tiirritella, placing the word Mathilda in 
brackets. The genus Mathilda was made to receive certain Tertiary fossils ; its 
family relationships are somewhat mixed, since it possesses the shell of a Tiirritella 
with the sinistral apex of the Pyramidellidm. 
As might be expected these long and slender shells are usually in a fragmentary 
condition, and for the most part the apertures are not preserved. The spiral 
ornamentation and peculiar axial cross-hatching, in addition to the great width of 
the sutural sulcus, may be regarded as characteristic of the section associated with 
the genus Mathilda. These fossils occur chiefly, if not entirely, in the Lower 
Division of the Inferior Oolite, and principally, as far as my experience goes, in 
Dorsetshire and Yorkshire. 
165. Turritella Dorsetensis, sp. nov. Plate XVII, flgs. I a, I 5, 1 c. 
Description : 
Spiral angle . 
Height of whorl to width 
Approximate length . 
Shell conical- elongate, inversely turrited. 
. 10 °. 
. 1 : 1-16. 
110 mm. 
Whorls about 30 ; these increase 
with great regularity, are slightly excavated, and provided with a prominent 
Carina a short distance above the suture Actual apex unknown. In the apical 
whorls the carina is relatively more prominent, and the position of the carina in 
some cases more median. The position of the carina varies considerably in 
different specimens, but is in all cases anterior, and in some mature specimens 
rather near the base of each whorl. The carinae are richly granulated by the 
cross-hatching, or axial ornamentation, which is very flne and close in this species. 
In the more apical whorls there are about four fine spirals above the carina and 
about two below, but this number increases with age, so that in some specimens the 
adult whorls have as many as seven spirals above and four below the keel, the latter 
being much crowded together. This represents the usual form (figs. I a, 1 c), but 
there is a variety (fig. 1 h) where the keel is more centrally situated, and where the 
