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 Murchisonce-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. Malaptera bentleyi, M. and L., var. neglecta. Plate III, fig. 2. 1 



Cf. Morris and Lycett, Great-Ool. Moll, pi. 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 — Spinigera, D'Orbigny, 1850. 



" These are Bostellarias compressed and with successive lateral varices, like 

 Ranella, but which have at each varix a long point.'''' ' Prod.,' vol. i, p. 270. Etage 

 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 Aporrhaidge, placed at the opposite extremity of the scale to that of 

 Malaptera and its allies. 



1 N.B. — This figure and fig. 1 c were drawn from reversed casts in gutta-percha. 



