RISSOINA. 273 
206. Rissoina optusa, Lycett, 1853. Plate XXI, figs. 10 a, 10d. 
1853. Ruissormva optusa, Lycett. Proc. Cottesw. Nat. Club, vol. i, p. 80. 
Bibliography, §c.—Lycett makes no mention of this species in the ‘ Cotteswold 
Hills,’ nor does Witchell enumerate any species of Rissoina in his ‘Geology of 
Stroud.’ It is not absolutely certain that the species under consideration is the 
one intended by Lycett, although his description tallies fairly. It must be 
allowed, however, that the name “obtusa” is unfortunate, as this is rather a 
slender shell. As a matter of fact an obtuse apex is characteristic of the genus. 
although the earlier authors speak of Rissoina as pointed. 
Description : 
Length . ; : : . 35 mm. 
Spiral angle about . econ 
** Spire obtuse ; whorls slightly convex, six ; ee lip moderately large ; cost 
numerous, closely arranged, slightly curved from left to right.””—Lycerr, loc. cit. 
Relations and Distribution.—Found sparingly in the Pea-grit at Crickley and 
Leckhampton. Lissoina Milleri, Lycett (Suppl., p. 18, pl. xliv, fig. 10), has some 
resemblance. 
207. RissoINA GYMNOIDES, sp. nov. Plate XXI, fig. 11. 
Description : 
Length . ; . 4mm. 
Height of body- hor to ee length . 3700, 008 
Spiral angle (obtuse) about. meer 
Shell subelongate, pupoid, scarcely eacrited. Whorls about six, smooth, 
convex, close; body-whorl about half the height of the entire shell. Aperture 
square in front and slightly canaliculate, lips only moderately thickened. 
Relations and Distribution.—At first sight this might seem to be some form of 
Pseudomelania, since the thickening of the peristome is less obvious than usual 
in Rissoina. But the pupoid character of the spire militates against this supposi- 
tion. It bears considerable resemblance to Rissoina gymna, Cossmann (Ait. Bath., 
p. 234, pl. xiv, figs. 23, 24), from which it differs in the greater relative length 
of the spire and in having a wider spiral angle. Four specimens are in my 
collection from the Lincolnshire Limestone of Weldon. 
35 
