BRITISH SILURIAN BRACHIOPODA. 215 



Genus — Crania, Retzitis, 178T. 



155. Crania Siluriana, Dav. Sil. Mon., PI. VIII, figs. 19, 20 ; Sil. Sup., PI. XVII, 



figs. 49—53. 



Since this species was described at p. 82 of the ' Silurian Monograpli,' Mr. John Gray, 

 of Hagley, discovered several exteriors and a very fine interior of this species attached 

 to a slab of Wenlock Limestone from Dudley. The specimen measured 5 lines in length 

 and slightly over 5 in breadth. The flattened margin is broad, and four muscular scars 

 are beautifully defined, the central pair being the largest. 



Specimens, also, of the exterior of a Crania which I cannot distinguish quite from 

 Crania Siluriana, v^ere collected by Mrs. R. Gray in the Middle Llandovery at Woodland 

 Point, and in the Lower Llandovery at Mullock Hill in Ayrshire. 



150. Crania Crofti, Dav. Sil. Sup., PI. XVII, figs. 54—56. 



Shell large, subquadrangular, or nearly circular, slightly indented anteriorly as well 

 as posteriorly ; upper or unattached valve conical and deep, with a deepest sinus or depres- 

 sion commencing at the extremity of the apex and occupying a large part of the anterior 

 half of the shell. Surface of valve covered with fine irregular radial strise ; in the interior 

 there is no flattened margin, the interior cavity sloping away rapidly from the outer edge; 

 under the posterior or inner edge are two small, oval-shaped, slightly-projecting muscular 

 prominences, separated by a short, rounded, longitudinal ridge, and further down, near 

 the centre of the valve, are two rather larger projections, formed by the adductor muscle ; 

 from the centre of the posterior margin the shell becomes convex, this convexity corre- 

 sponding to the depression on the exterior of the valve; lower or attached valve not 

 known. 



Two specimens measure — length 13, width 15, depth 7 lines ; length 5, width 6, 

 depth 3^ lines. 



Obs. — Of this fine large Crania Mr. C. Croft found two or three examples in the 

 Caradoc at Ty-Isaf, Llansantffraid, in Wales. It is only slightly smaller than Crania 

 Itlii/choltiana, de Koninck, from the Lower Carboniferous Limestone of Ireland, the 



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