﻿Vol. 6 1.] THE SILURIAN SOCKS OF LLANGADOCK. 569 



species here described, and also than the type of Bembeocia ; there- 

 fore Pleurotomaria Lloydii may eventually have to be placed in a 

 new and separate genus. I shall be able to decide this point 

 better, when I have had time to study the numerous specimens from 

 other localities. 



Genus Plethospira, Ulrich. 

 Subgenus Ulrichospira, nov. 



Diagnosis. — Shell subcorneal; whorls about five, moderately 

 convex, subangular at the periphery where the band is situated. 

 Band concave, bounded on each side by a strong keel. Ornamen- 

 tation sometimes consisting of accessory keels. 



Type. — Ulrichospira similis, sp. nov. 



Hem arks. — This subgenus differs from Pletliospira in having 

 less convex whorls, and in sometimes being ornamented by keels 

 in addition to those bounding the band. 



Ulrichospira simtlis, sp. nov. (PI. XXXVII, fig. 3.) 



Diagnosis. — Shell small, subcorneal, composed of more than 

 three whorls. Whorls increasing at a moderate rate, somewhat 

 convex, but with a slight angularity at the periphery where the 

 band is placed. Band submedian, rather concave, bounded on each 

 side by a prominent keel. Ornamentation consisting of a slight 

 ridge just below the suture, a fainter one between this and the band, 

 and a strong keel below the band, which appears immediately above 

 the suture on the earlier whorls: above this keel is a narrow groove. 

 Lines of growth sharp and distinct, making an acute angle on the 

 upper ridge, then forming a strongly-concave curve in their back- 

 ward sweep to the band, but slightly curved on the band itself and 

 passing downwards almost vertically ; closer together on the base. 

 Aperture unknown. 



Remarks and Resemblances. — There is but one known 

 specimen of this species. It greatly resembles Murchisonia pulchra, 

 M'Coy, 1 but may be distinguished by the band being grooved instead 

 of being prominent in the middle, by the bordering keels being 

 stronger, by the upper ridge being more marked, the lines of growth 

 making more concave curves, and by the presence of a narrow 

 groove above the lower keel. The lines of growth appear to indi- 

 cate a sinus rather than a slit in the outer lip ; consequently this 

 species cannot be regarded as a true Pleurotomaria. 



Dimensions. — Length = 10 millimetres; width = 8 mm. 



Horizon. — (17) Upper Llandovery. 



Bembexia, (Ehlert. 



Bembexia (?) Groomii, sp. nov. (PI. XXXVII, fig. 4.) 



Diagnosis. — Shell very small, conical, consisting of more than 

 five whorls. Whorls but slightly convex, subangular at the 



1 Synopsis of the Silurian Fossils of Ireland ' 1846, p. 16 & pi. i, fig. 19. 



