870 DR F. R. C. REED ON THE 



apical foramen in the pedicle-valve is sometimes present, as Davidson showed 

 (pi. xli, fig. 5). The examples from the Balclatchie Group have more numerous 

 riblets than those from the Stinchar Limestone Group, but otherwise seem identical. 

 The interior of the pedicle-valve has only been seen in a specimen from Balclatchie. 

 It does not appear probable that the fossil described by Brogger * as Strophomena 

 imbrex, var. cf. semiglobosa, from Norway, is identical. 



Rafinesquina ? brumalis, sp. nov. 

 (Plate XII, figs. 21-24.) 



Shell small, semielliptical to subquadrate, sometimes nearly as long as wide, 

 flattened, compressed, plano-convex ; hinge-line straight, equal to or slightly less 

 than maximum width of shell ; cardinal angles rectangular or slightly obtuse, not 

 produced. Pedicle- valve very gently convex near beak, elsewhere nearly flat ; beak 

 small, pointed, acute, rising a little above hinge-line, not incurved. Brachial valve 

 flat or slightly concave ; beak inconspicuous, not projecting. Interior of valves 

 unknown. Surface of shell ornamented with about 30 primary equidistant regular 

 thread-like radii, curving back rather strongly on each side of middle line, with a few 

 shorter secondary similar radii ; interspaces flat, holding 3-5 very delicate radial lines 

 and crossed by minute close low non-continuous concentric wrinklings and striae. ' 



Dimensions. — Length, 8 '5 mm. ; width, ll'O mm. 



Horizon. — Balclatchie Group. 



Locality. — Balclatchie. 



Remarks. — This small shell is rather rare. It differs from R. subarachnoidea 

 (described below) by its more subquadrate shape, rectangular cardinal angles, more 

 numerous and curved radii, and finer concentric markings. It is more allied to Sir. 

 arachnoidea, Tornquist,f in shape, ornamentation, and small acute projecting beak. 



Rafinesquina' 1 . subarachnoidea, sp. nov. 

 (Plate XII, figs. 25-31.) 



1870. Strophomena corrugatella, Davidson (pars), Mori. Brit. Foss. Brack., vol. iii, pt. vii, pi. xli, 



fig. 12 (cet. excl.). 

 1883. Strophomena corrugatella, Davidson (pars), ibid., vol. v, Silur, Suppl., p. 192, pi. xv, figs. 23, 



24, 26 (non fig. 25). 



Shell semicircular to subsemicircular, much compressed, flattened or concavo- 

 convex to plano-convex, alate or subalate, nearly twice as wide as long ; hinge-line 

 equal to maximum width of shell, with acutely pointed slightly produced cardinal 

 angles. Pedicle-valve fiat or very gently convex ; beak pointed, small, acute, rather 

 prominent, projecting a little, not incurved ; hinge-area narrow, with small convex 



* Brooger, Die Silur. Etagen 2 und 3 (1882), p. 50, t. xi, fig. 6a. 

 t Lindstrom, Fragm. Silur., p. 29, t. xiv, figs. 41, 42. 



