THE SINISTRAL GROUP. 301 
Fig. 7 represents a specimen from the Cotteswolds in much better preservation 
than the type (fig. 6); this has also rather a smaller spiral angle, and has probably 
developed an additional whorl. 
Relations and Distribution.—* Littorina”’ recteplanata seems generically related 
to certain cylindro-conical forms of Amberleya which are rather characteristic of 
the Lias. It is extremely rare. In the Inferior Oolite, besides the type, I know 
of one specimen from Dundry and two from the Pea-grit of Longfords. Cf. also 
* Monodonta” imbricata, Morr. and Lye., ‘Grt. Ool. Moll.,’ pt. 1, p. 67, pl. xi, fig.§3. 
237. Lirrorina (? Trochus) vrrarmata, Hébert and Deslongchamps, 1860. Not 
figured. 
1860. Trocuus TRIaRmatus, Héb. and Desl. Foss. Montreuil-Bellay, p. 62 (sep. 
copy), pl. iii, fig. 5. 
A single specimen of this well-marked cylindro-conical form has come under 
my observation ; it is somewhat longer and narrower than the type, but possesses 
the characteristic ornamentation. 
It is apparently from North Dorset, and not improbably from the concavus- 
zone of Bradford Abbas. In this case it may be an extreme “sport” of the poly- 
morphous Littorina Dorsetensis. 
Tue SrnistRaL Grove. 
This group comprises a number of shells which have been described under 
Cirrus, Hamusina, Scevola, and perhaps Tectus, the three last-named genera 
having been constituted by Gemmellaro for the reception of species of this group 
which occur in the Lias-Oolite of Sicily. Besides the common feature of being 
sinistral, most of them are characterised by rugose ornamentation, by possessing a 
shell more or less trochiform or turbinate, and in the case of Hamusina rather 
thin. The aperture is circular, and there is scarcely any columella. Some 
species, such as Cirrus nodosus, Sowerby, have an enormous umbilical excavation, 
whilst in Hamusina the closure is complete. Nevertheless the presence or absence 
of an umbilicus is probably not of much generic importance, though we may 
make use of it for purposes of separating, for instance, Hamusina from Cirrus. 
This group, to judge from Gemmellaro’s work, is evidently well represented in 
the Lias-Oolite of Sicily. It is also fairly abundant in the lower division of the 
