(2) 



(3) 



26 



22 mm. 



33 



27 mm. 



ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 903 



somewhat flattened disc, subgeniculate, concavo-convex ; cardinal angles slightly 

 flattened, pointed, and produced. Pedicle-valve concave, generally produced in 

 front into short blunt tongue ; interior of valve with short subcircular well-defined 

 muscular area with sharp raised edges, extending about one-fourth the length of valve, 

 composed of a pair of contiguous fiabelliform diductors. Brachial valve gently 

 convex, with more or less flattened ill-defined disc and bent-down margins ; cardinal 

 process bilobed, deeply cleft, set on thick hinge-plate ; crural plates short, stout, 

 inclined at about 30° to hinge-line ; muscle-scars well marked, deep, the posterior 

 adductors subcircular, rather wide apart, and the anterior pair longer, elongate-oval. 

 Surface of valves covered by rather coarse angular straight or slightly curved ribs of 

 unequal and irregular size varying in number and increasing by intercalation at 

 irregular intervals of smaller ribs of unequal size, all rugose and crossed by con- 

 centric striations, more or less coarse. 

 Dimensions. — 



(1) 

 Length . . . .29 



Width . . . .34 



Horizon. — Saugh Hill Group. 



Locality. — Woodland Point. 



Remarks. — This form is a well-marked variety and is abundant at Woodland 

 Point. It approaches most nearly the Wenlock variety scabrosa, Davidson,* but 

 the ribs in the Girvan variety are not so numerous nor so regular, and are also 

 coarser and more variable in size, while the scabrous concentric lamellae are less 

 developed. The presence of a more or less definite disc and of the tongue-like 

 projection in front are additional points of difference. The internal characters, how- 

 ever, are essentially the same as Davidson figured for his var. scabrosa, so that it 

 can only be regarded as a local variety. 



Strophomena deficiens, sp. nov. 

 (Plate XIX, figs. 6-10.) 

 Shell semielliptical to subquadrate, concavo-convex to plano-convex, much com- 

 pressed, widest at hinge-line ; cardinal angles rectangular. Pedicle-valve gently 

 concave to nearly fiat, slightly swollen near beak; beak small, pointed, rather 

 retrorse, not incurved ; hinge-area of moderate width, triangular, steeply inclined 

 to plane of valve, with large broad triangular delthyrium covered by convex plate ; 

 interior of valve with pair of short small teeth on thin dental plates, posteriorly 

 defining transverse subcircular short muscle-area, about one-third length of valve, 

 composed of a pair of contiguous fiabellate short radially ridged diductor scars 

 feebly denned in front; weak submarginal concentric ridge occasionally present 

 near edge of valve. Brachial valve gently convex; beak small, inconspicuous; 



* Davidson, op. tit., vol. iii, p. 299, pi. xliv, figs. 10-13. 



