ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 945 



and wider and the interior shows a short median septum. It is somewhat allied to 

 Z. Hicksi, Reed, # from the Slate Beds of Haverfordwest. 



Zygospira ? sp. 

 (Plate XXIV, figs. 28, 29.) 



One internal cast and external impression of a pedicle-valve from the Starfish 

 Bed bears a considerable resemblance to the species Zygospira cincinnatiensis, 

 Meek,t from the Lorraine Group. Our specimen measures just over 9 mm. in length 

 and the same in width, being subcircular in shape ; there is a low indistinct median 

 fold with a narrow deep depression along its middle holding 2 ribs which arise from 

 the bifurcation of one near the beak ; on each side of this depression the fold 

 bears 3 rather broader rounded ribs, with a very short narrower one intercalated 

 close to the margin alongside the depression. The lateral portions of the valve 

 each carry 8-9 similar rounded ribs, of which balf arise by intercalation at rather 

 more than one-third their length. The short thin dental plates are visible in 

 the cast. 



The species appears to lie between Z. cincinnatiensis, Meek, and Z. putilla, Hall 

 and Clarke. I 



Horizon. — Drummuck Group (Starfish Bed). 



Locality. — Thraive Glen. 



Genus Protozyga, Hall and Clarke. 



Protozyga carrickensis , sp. nov. 



(Plate XXIV, figs. 30, 31.) 



Shell subpentagonal, unequally biconvex, widest across middle, rounded, anteriorly 

 emarginate, and sinuated. Pedicle-valve convex, swollen, subcarinate, highest 

 along middle line, with short broad shallow groove on keel near anterior margin ; 

 beak small, pointed, incurved, rising above hinge-line, with apex perforated, and small 

 triangular broad fissure below. Brachial valve weakly convex or flattened, bilobed 

 by narrow median straight impressed line and by broad indefinite sinus near 

 anterior margin ; beak small, inconspicuous. Surface of valves smooth. Interior 

 unknown. 



Dimensions. — Length, 11 mm. ; width, 11 mm. 



Horizon. — Stinchar Limestone Group. 



Locality. — Craighead. 



Remarks. — This interesting little shell, of which I have only seen two specimens 

 in Mrs Gray's collection, closely resembles Protozyga exigua, Hall,§ of the Trenton 



* Reed, Geol. Mag., dec. v, vol. ii, 1905, p. 452, pi. xxiii, figs. 17-19. 



t Meek, Paleeont. Ohio, i, 1873, p. 126, pi. 11, fig. 5 ; Hall and Clarke, op. cit., Brack, ii, pi. liv, figs. 13, 14. 



% Hall and Clarke, op. cit., pp. 157, 365, pi. liv, figs. 35-37 ; pi. lxxxiii, figs. 29, 30. 



§ Hall and Clarke, op. cit., Brack, ii, p. 151, pi. liv, figs. 47, 48. 



