STROPHOMENIDiE. 301 



From the Llandovery. — I have seen examples from Haverfordwest; Mathyrafal 

 Pen-y-Craig ; Llangynwy ; Gas- Works, Haverfordwest ; all Lotoer Llandovery. In the 

 Upper Llandovery it was found at Penlan, Llandovery, by Mr. Hughes. It occurs also 

 at Bogmine. 



The Wenlock Limestone and Shales, however, appear to be its principal place of 

 abundance. It is not very rare at Benthall Edge, near Walsall, and at Woolhope, 

 Wenlock Edge, Dudley, Rock Farm (May Hill), Longhope, and Dormington Wood, 

 Penlan, Cardiff, &c. 



In the Lower Ludloio at Ledbury, &c. 



In Scotland at Penkill, Ayrshire (Llandovery), and the Pentland Hills (Wenlock 

 Shales). 



It is also stated to occur in Ireland ; but I have not seen any Irish specimens. 



Abroad it occurs in Gothland. The specimens described by Mr. Billings from 

 Anticosti do not appear to belong to the Sowerbyan shell. 



Strophomena corrugatella, Bav. PI. XLI, figs. 8 — 14. 



Oethis corrugata, Portlock (not of Conrad). Rep. Geol. Londonderry, &c., p. 4.50, 

 pi. xxxii, figs. 17 and 18, 1843. 

 — UNDULATA, iTf'Coy (not of Vanuxem). Synop. Sil. Foss. Ireland, p. 36, pi. iii, 

 fig. 22, 1846. 



— CORRUGATA, Phillips and Salter. Mem. Geol. Survey, vol. ii, p. 291, 1848. 

 Lept^na — Barrande. Sil. Brach. Bohmen ; Naturw. Abbandl., vol. ii, pi. 



xxi, fig. 16, 1848. 



— — M'Co]/. Brit. Pal. Foss., p. 233, 1852. 



Spec. Char. Semicircular, wider than long ; hinge-line slightly exceeding the width of 

 the shell, with slightly rounded acute-angular cardinal extremities ; sides and front 

 regularly rounded. Ventral valve moderately convex ; area narrow ; fissure small, arched 

 over by a pseudo-deltidium ; beak not projecting. Dorsal valve gently concave, but in 

 some examples slightly convex or raised along the middle (fig. 10). Hinge-area linear. 

 External surface radiated by a greater or lesser number of strong, narrow, prominent, 

 thread-like riblets, with wide interspaces between the pairs. The number of riblets 

 increases at variable distances from the beaks, by the interpolation of a smaller rib ; and 

 the whole interspace is furrowed with from four to seven fine longitudinal striae. In 

 addition to these, the entire surface between the longitudinal ribs is crossed by zigzag 

 concentric irregular wrinkles, which vary in thickness according to the specimen. Interior 

 not well known. 



Length 10, width 15, depth 2 lines. 



Obs. This beautiful species varies considerably in its external appearance, on account 



