102 GASTEROPODA OF THE INFERIOR OOLITE. 
increasing ratio. The anterior portion of the wing is ornamented by numerous fine 
lines. The principal digitations are six, but a subordinate seventh occurs. 
The aperture is short and nearly quadrate; the six or seven furrows of the 
wing, corresponding to the digitations, radiate from the outer lip, and the posterior 
furrows communicate directly with the aperture. The canal is very wide at first, 
but tapers gradually to a tolerably fine groove, as the anterior spine, or canal- 
sheath is bent back almost in the form of a sickle. 
Relations and Distribution.—This species is of considerable interest as probably 
the oldest Malaptera known. The Collyweston Slate cannot well be higher than 
the middle part of the Murchisone-zone. Poor specimens are occasionally obtained 
from the neighbouring Lincolnshire Limestone, but the species has probably not 
been found out of the Stamford district. It is by no means uncommon at Colly- 
weston. 
21. Mataprera BenTLEYI, M. and L., var. Npcuncta. Plate ITI, fig. 2.’ 
Cf. Morris and Lycett, Great-Ool. Moll., pl. iii, fig. 16. 
This differs from the more usual form, (1) in being smaller, (2) the whorls of 
the spire being rather more angular and the ornamentation finer ; (3) the posterior 
digitation more recurved upon the spire; (4) the anterior digitations scarcely 
perceptible. 
Genus—Spinicgera, D’ Orbigny, 1850. 
“These are Rostellarias compressed and with successive lateral varices, like 
Ranella, but which have at each varix a long point.’ ‘ Prod.,’ vol. i, p. 270. Ktage 
Bajocien.’ 
Fischer (‘ Manuel,’ p. 677) regards Spinigera as merely a subgenus of Alaria. 
He gives the following diagnosis. ‘ Shell elongate, narrow, fusiform ; anterior 
canal long, straight ; varices continuous, aligned on one side or on both sides, as 
with Ranella, and provided with a long spine directed transversely.” The com- 
pression of the shell, originally diagnosed by D’Orbigny, seems to me also an 
important feature, and helps to distinguish Spinigera, which represents a curious 
section of the Aporrhaide, placed at the opposite extremity of the scale to that of 
Malaptera and its allies. 
1 N.B.—This figure and fig. 1 ¢ were drawn from reversed casts in gutta-percha. 
