296 BRITISH SILURIAN BRACHIOPODA. 



Strophomena Jukesii, Dav. PI. XXXVII, figs. 23—26. 



Spec. Char. Semicircular, longer than wide, broadest at the hinge-line, with snoall 

 mucronate wings. Ventral valve moderately convex, exterior marked by numerous 

 exceedingly fine, radiating lines. Area triangular, of moderate breadth, and divided 

 in the middle by a narrow convex pseudo-deltidium. In the interior the two small 

 teeth for the articulating of the valves lie close to the hinge-line, on either side, at the 

 base of the deltidium ; the saucer-shaped muscular area occupies a space of about one 

 fourth of the width of the shell ; the vascular impressions are sharply defined, and 

 consist of two principal trunks, of which the external branches are turned outwards and 

 backwards, enclosing wide ovarian spaces, as well as the elevations formed by the mantle 

 pressing upon the horizontally coiled spiral arms. On the side facing the margin of the 

 valve the vascular trunks (above described) give off smaller bifurcated branches, which 

 extend to the edge of the shell. Dorsal valve not known. 

 Length 10, width 15 lines. 



Obs. Of this curious shell only a very few examples of the ventral valve have been 

 hitherto discovered, and these chiefly under the condition of sharply marked internal 

 casts. One curious feature of this shell is the coiled impressions left by the spiral arms, 

 which bear some resemblance to those we find in certain Swedish examples of Strophomena 

 rhomboidalis (see PI. XXXIX, fig. 16). 



Position and Locality/. Mr. Baily informs me that he has paid two visits to the 

 quarry at Grangegeeth, County Meath (Ireland), where Strophomena Jukesii is found, 

 and that he attributes the rock to the Caradoc-Bala period. This remarkable species 

 is named in honour of the late distinguished Director of the Geological Survey of 

 Ireland. 



Strophomena arenacea, Salter, MS. PI. XLII, figs. 6 — 8. 



Strophomena arenacea, Salter, MS. Cat. Mus. Prac. Geo)., p. 36, 1865 (neither 



figured nor described). 



— — Id., MS. Mem. Geo). Survey, vol. iii, p. 361, 1866. 



— — Bigsby. Thesaurus Siluricus, p. 121, 1868. 



Spec. Char. Semicircular, widest at the hinge-line, with short semicylindrical ears ; 

 sides and front broadly rounded. Ventral valve convex ; hinge-area narrow ; beak small, 

 incurved, scarcely projecting. Dorsal valve concave, following the curves of the opposite 

 one. Surface of both valves marked by numerous, very fine, thread-like radii, with 



