322 MISS DONALD ON PROTEROZOIC GASTEROPODA [ May rgo2, 
(Ehl. than any other: consequently I place it there provisionally. 
M. (Ehlert does not state whether the forms grouped in this Section 
possess a slit or a sinus. | 
Dimensions.—The type (Pl. VII, fig. 2) has the apex broken ; 
the six remaining whorls measure 13 millimetres in length and 5mm. 
in width. The specimen marked M. gracilis (Pl. VII, fig. 3) has 
portions of six whorls preserved, in a length of 14mm. An example 
(Pl. VII, fig. 4) with exsert whorls, in the Cardiff Museum, has 
about eight whorls in a length of 23 millimetres. 
Localities and Horizon.—The specimens in the Bristol 
Museum are from the Ctenodonta-bed in the Rhymney Grit, 
Rhymney Hill, Cardiff, and are of Lower Wenlock age. Those in 
the Cardiff Museum are in the Storrie Collection, from Tymaur 
Lane, Rhymney, near Cardiff; and the rock in which they occur is 
similar to that just mentioned. 
Subgenus CyrTosrROPHA, nov. 
Diagnosis.—Shéll elongated, conical, composed of numerous 
whorls. Whorls more or less convex, slightly flattened above, 
eenerally with a prominence or subangularity between the upper 
suture and the band. Band grooved, bordered on each side by a 
raised thread or keel, submedian, and situated on the widest part 
of the whorl. Lines of growth curving back to, and forward from, 
the band with a moderate degree of obliquity, more oblique below, 
and forming crescents on the band itself. Ornamentation consisting 
of spiral lines and a shallow groove immediately above the band. 
Aperture subovoid. Columella nearly straight. 
Type, Cyrtostropha corallii (Sow.). 
Remarks and Resemblances.—This subgenus differs from 
the typical Murchisona in its more convex whorls and more 
oblique lines of growth, especially below the band, and probably in 
the presence of a sinus instead of a slit in the outer lip. None of 
the specimens with which | have met have the aperture well pre- 
served, so it is impossible at present to determine this latter point. 
Cyrtostropha greatly resembles Hormotoma in the convexity of its 
whorls, but is distinguished by the less oblique lines of growth 
and the spiral and grooved ornamentation. 
Dimensions.—The length varies from about 6 to 36 millimetres. 
Range.—From the Bala Formation up to and throughout the 
Silurian Period. 
CyRTOsTROPHA CORALLII (Sow.). (Pl. VII, figs. 5 & 6.) 
Pleurotoma corallii, J. de C. Sowerby, 1839, ‘ Sil. Syst.’ p. 612 & pl. v, fig. 26. 
Murchisonia corallii, A. @Archiac & E. de Verneuil, 1841, Bull. Soc. Géol, 
France, vol. xii, p. 160; ? F. M‘Coy, 1846, ‘Syn. Silur. Foss. Ivel.’ p.16; J. Phillips, 
1848, Mem. Geol. Surv. vol. ii, pt. i, ‘Malvern Hills’ p. 258; H. G. Bronn, 1848, 
‘Index Paleont.’ pt. i, p. 747; A. d’Orbigny, 1850, ‘ Prodr. de Paléont. Strat.’ vol. i, 
p.31; J. Morris, 1854, ‘ Catal. Brit. Foss.’ 2nd ed. p. 259; J. Sowerby, 1867, Siluria ” 
4th ed. pl. xxiv, fig. 7 & p. 532; J. J. Bigsby, 1868, ‘ Thes. Silur.’ p. 158; A. C. 
Ramsay, 1881, Mem. Geol. Surv. vol. iii, ‘Geol. N. Wales ’ 2nd. ed. p. 468; J. D. 
La Touche, 1884, ‘ Geol. of Shropshire’ p. 80 & pl. xviii, fig. 634; R. Etheridge, 1888, 
‘ Foss. Brit. Is.’ vol. i (Paleozoic) p. 113. 
