PILEOLUS. 337 
Genus—PiLnoLus, G. B. Sowerby, 1823. 
Shell limpet-like above, with a subcentral apex ; concave beneath, with a narrow 
semilunar aperture, having a raised border and a columellar disc, surrounded by a 
broad and continuous peristome. Apex not spiral; shell provided with a columellar 
septum. 
According to the original diagnosis of this singular genus, Sowerby regarded it 
as possessed of a short internal spire, and this statement is repeated by Morris 
and Lycett. There does not seem any reason, however, to suppose that Pileolus 
possessed an internal spire, although the plications shown in the enlarged section 
(Pl. XXVITI, fig. 16) in the region to the left of the columellar septum are some- 
what imitative of one. 
Fischer speaks of the apex as being subcentral, not spiral. Mr. B. B. Wood- 
ward also, in a recent communication to the Zoological Society,’ observes that 
this genus most clearly possesses a septum, as in Neritina crepidularia and Tomo- 
stoma, and that there is no true internal spire. 
270. Piteo.us puicatus, G. B. Sowerby, 1823. Plate XXVIII: var. A, figs. 13 a, 
13); var. B, figs. 14a—c. En- 
larged section, fig. 16. 
1823. PineoLus puicatus, G. B. Sowerby. Genera of British Shells, No. 19, 
figs. 1—4. 
1823. _— _— J. Sow. Main. Conch., pl. eceexxxii, figs. 1—4. 
1851. _ — Sow. Morris and Lycett, Great Ool. Moll., pt. i, 
p- 60, pl. ix, figs. 36, 36 a—e. 
1854. = — G. Sow. Morris, Cat., p. 268. 
? Syn. Parerta cosrutara, Miinst. Goldf., Petref. Germ., pl. clxvii, fig. 9. 
Bibliography, §c.—The type of Pileolus plicatus was obtained from the Great 
Oolite of Ancliff; the species is also well known, though far from common, in the 
Great Oolite of Minchinhampton. Morris quotes both this and P. levis from the 
Inferior Oolite of the same district, and other authors, including Witchell (‘ Geology 
of Stroud,’ p. 47), make mention of these two species as occurring in the Inferior 
Oolite of the Cotteswolds. I have not seen specimens from the Cotteswolds, but 
the specimens from Lincoln, figured in the accompanying plate, differ consider- 
ably from the form prevailing in the Great Oolite of Minchinhampton. 
1 “Qn the Mode of Growth and the Structure of the Shell in Velates conoideus, Lamk., and 
other Neritide,’”’ ‘Proc. Zool. Soc.,’ June 14th, 1892. 
