908 DR F. R. C. REED ON THE 



the edge. Riblets and interspaces crossed by very fine inconspicuous concentric 

 striation. Substance of shell finely punctate. 



Dimensions. — 



(1) (2) (3) (4) (Davidson's type.) 



Length .... 34 39 21 33 mm. 



Width .... 43 51 27 45 mm. 



Horizon. — Saugh Hill Group. 

 Localities. — Woodland Point, Newlands. 



Remarks.— Davidson referred these shells to " Strophomena" pecten (Linn.),* but 

 they differ from this species firstly and principally by their distinct ornamentation, 

 and secondly by the more rectangular shape of the cardinal angles, shorter hinge- 

 line, and absence of strong concentric lineation. The species seems more to resemble 

 Sch. tenuis (Hall) t of the Niagara Group. 



Genus Triplegia, Hall. 



Triplecia craigensis, sp. nov. 



(Plate XX, figs. 4, 5.) 



1883. Rhynchonella baleletehiensis, Davidson (pars), Mon. Brit. Foss. Brach., vol. v, Silur. Suppl., 

 p. 200, pi. xi, figs. 23a-d. 

 Non 1883. Rhynchonella baleletehiensis, Davidson, ibid., p. 160, pi. x, figs. 15, 16. 



Shell transverse, widest across middle, broader than long, subelliptical, with 

 strong angular median fold on brachial valve and corresponding sinus on opposite 

 valve, and deeply sinuated anterior edge, usually emarginate ; hinge-line straight, 

 short, about one-third width of shell. 



Pedicle-valve gently convex, shallow, with angular median sinus arising at about 

 half the length of valve and rapidly increasing in depth and width to front margin ; 

 edges of sinus sharply angular ; lateral lobes flattened ; beak small, acute, rising- 

 above hinge-line, with apical foramen ; hinge-area small, triangular, slightly concave, 

 steeply inclined, with median triangular delthyrium. Brachial valve swollen, carinate, 

 with strong median fold rising a little in front of beak and rapidly becoming sub- 

 angular or angular, rising high above lateral lobes on front margin, and sharply 

 marked off from them ; lateral lobes gently swollen, dependent ; beak small, rounded, 

 incurved, lower than that of opposite valve. Surface of lateral lobes of brachial 

 valve marked with about 15 fine faint equidistant thread-like radial lines, slightly 

 curved back on each side ; fold of brachial valve and whole of pedicle-valve covered 

 with very fine concentric lineation. Interior unknown. 



Dimensions. — 



(1) (2) 



Length . . . . .12 11 mm. 



Width 18 14 mm. 



* Davidson, op. cit., vol. iii, p. 304, pi. xliii, figs. 1-11. 



t Hall, 11th Ann. Rep. State Geol. Indiana, 1882, p. 287, pi. xxiii, figs. 11-13. 



