298 BRITISH SILURIAN BRACHIOPODA. 



every fifth, seventh, or ninth of the strise larger than the others ; but near the beak 

 they often seem simply alternate in size, the intervening delicate sulci closely punctured " 

 (M'Coy). 



Length 12, width 18, depth 1 line, 

 Obs. I am not well acquainted with this species, not having been able to procure 

 satisfactory specimens of the shell ; so I have reproduced Prof. M'Coy 's description and 

 figures. That Palaeontologist has further observed that his species, in size, form, 

 striation, and tubular perforation of the apex of the beak, almost exactly resembles 

 Leptana alternata of Conrad, but diSers from it in having the ventral or foraminated valve 

 concave, instead of convex ; the striation is also finer, flatter, and more uniform ; and 

 these features, together with the greater deflection or arching of the valves, also separate 

 it from Strophomena grandis (M'Coy). 



Position and Locality. Strophomena simulans, as far as we at present know, is re- 

 stricted to the Caradoc and Upper Llandovery (?) formations ; and is said to be not 

 uncommon in the Bala Schists of Blain-y-Cwm, west of Nantyre, Cefn Coch, Glyn 

 Ceiriog, Denbighshire ; and in the OUve Schists of Goldengrove, Llandeilo, Caermarthen- 

 shire. At p. 361 of vol. iii of the ' Geol. Survey ' it is recorded from the Upper 

 Llandovery at Malvern, but this identification still requires confirmation. 



In the Museum of the Geological Survey of Ireland are specimens from Carrickadaggan, 

 County Wexford, and from Knockmahon, Tramore. 



Strophomena (?) RETROFLEXA, Salter. PI. XLII, figs. 15 — 17. 



Orthis RETROFLEXA, Salter, MS., (not of Pander). Catal. Fossils Mus. Pract. Geol., 

 p. 8, 1865. 



Spec. Char. Broadly semicircular, wider than long, greatest width at the hinge- 

 line; cardinal extremities forming small mucronate wings; lateral and frontal margins 

 rounded. Ventral valve moderately convex, without fold or sinus ; area triangular, about 

 nine times as long as high ; fissure narrow, arched over by a pseudo-deltidium. Dorsal 

 valve flat or slightly convex ; hinge-area narrow, one fourth as wide as the ventral one. 

 Surface of valves ornamented by very numerous, fine, thread-like radii, with a shorter 

 and finer rib interpolated between each pair of the larger ones. Interior of valves 

 not known. 



Length 6, width 7^, depth 3 lines. 



Obs. On a tablet in the Museum of Practical Geology this species was erroneously 

 labelled "0.r<?^ro/?e'a?a= .'' Gonamhonites retroflexa. Pander." The Russian author's species 

 is, however, quite distinct, both in characters and shape, from the shell under description, 

 and does not belong to the same genus. I have therefore retained the name retroflexa, 



