BRITISH SILURIAN BRACHIOPODA. 193 



gently concave, area narrow but wider than that of the opposite valve, fissure partly 

 arched over by a small pseudo-deltidium. Surface of valves finely radiatedly striated, 

 with shorter ribs interpolated between the longer radii ; valves crossed by a few concentric 

 lines of growth. Two specimens measured 



Length 12, breadth 18, depth ]i lines; length 11|, breadth 17, depth 2| 

 lines. 



Ohs. — Internal casts and impressions of the exterior were collected by Mr. J. Parrott 

 from the Upper Caradoc or Cynwyd Beds, Trystion Valley, near Corwen, in Merionethshire. 

 In this species the ventral valve is slightly concave, and the dorsal valve is convex. It is 

 remarkably regularly semicircular. 



Similar specimens with the shell preserved were also found by Mrs. R. Gray in the 

 Middle Caradoc at Shallock Mill, in Ayrshire. 



117. Strophomena antiquata. Sow. Dav., Sil. Mon., PI. XLIV, figs. 2 — 13, and 21, 



22 ; Sil. Sup., PI. XV, figs. 12—14. 



In Scotland Strophomena antiquata is very abundant in the Middle Llandovery, at 

 Woodland Point ; also in the Upper Llandovery or Penkill Beds, at Bargany-Pond Burn, 

 at Penkill ; and at Penwhapple Glen, in Ayrshire. I give figures of some fine examples 

 collected by Mrs. R. Gray in those localities ; and, as we have stated elsewhere, it is found 

 in the Wenlock series of the Pentland Hills. 



118. Strophomena Callawayiana, Lav. Sil. Sup., PI. XVI, figs. 6, 7. 



Shell longitudinally semicircular, longer than wide, hinge-line as long as the breadth 

 of the shell; ventral valve geniculated, flattened portion traversed by concentric 

 wrinkles, surface finely striated ; dorsal valve following the curves of the ventral valve. 

 Length 13, breadth 10 lines. 



Obs. — Of this species two examples were procured by Dr. C. Callaway from the 

 Caradoc at Marsh Brook and Gretton. 



119. Strophomena ? bipartita, Salter. Dav., Sil. Sup., PI. XVI, figs. 9 — 12. 



Stuophomena bipartita, Salter. Quarterly Journal Geol. Soc, vol. x, p. 74, 1854. 



Shell marginally transversely semicircular, wider than long, hinge-line as long as the 

 breadth of the shell ; dorsal valve gently convex, divided into two lobes by a deep angular 



