804 DR F. R. C. REED ON THE 



of the pedicle-valve seems rather more pointed and acuminate than in the typical 

 Tyrone form, and the whole shell is rather narrower and more lanceolate, and some 

 of the concentric ridges on the surface are stronger than others. The average 

 dimensions are under 5 mm. in length ; one specimen measures 4 '4 mm. in length 

 and 2 '5 mm. in width. Portlock says, with regard to his Tyrone examples of 

 L. brevis,. that the external concentric lines of growth are very fine, and that the 

 length is to the breadth as 5:4. From the narrower shape of our shell we may 

 term this variety angustior. 



Horizon. — Balclatchie Group. 



Localities. — Balclatchie, Dow Hill, Ardmillan. 



Lingula brevis, Portlock, var. nov. carrickensis. 



(Plate II, figs. 11-13.) 

 1883. Lingula brevis, Portlock, Davidson, Mon. Brit. Foss. Brack., vol. v, Silur. Suppl., p. 224. 



Shell oval, widest across middle, unequally biconvex, subtruncate anteriorly. 

 Pedicle-valve strongly convex, almost inflated, most so towards beak ; beak swollen, 

 pointed, slightly incurved ; shoulders short, ill defined, meeting at about 75°-90° at 

 beak. Brachial valve less convex and shorter than pedicle-valve. Surface of shell 

 ornamented by very delicate concentric striae, with occasionally a few stronger 

 growth-ridges, and some very fine and faint radial striae. Interior unknown. 



Dimensions. — Length, 4'4 mm. ; width, 3'0 mm. 



Horizon. — Whitehouse Group. 



Locality. — Whitehouse Bay. 



Remarks. — This little shell is rather common at Whitehouse Bay, but I am not 

 at all satisfied that it is identical with L. brevis, Portlock. # The swollen nature of 

 the pedicle-valve is unusual, and the faint radial striae which are occasionally visible 

 are peculiar. But in outline the shell seems practically indistinguishable. David- 

 son labelled these shells as " L. brevis, I think," so that he evidently entertained 

 some doubt as to their specific identity. Portlock described the surface of his 

 species as " flattened," and stated that the shell had a " short wide aspect." This 

 does not agree with our specimens. 



Lingula ? crumenoides, sp. nov. 

 (Plate II, fig. 14.) 



Shell subcuneiform, rounded, increasing in width anteriorly, subequally biconvex. 



Pedicle-valve with slightly prominent and pointed beak, the shoulders sloping 



away at about 75°-80° for less than one-fourth length of shell, making very 



obtuse angle with sides ; interior of shell with large scattered pits and a faint longi- 



* Davidson, op. cit., vol. iii, pt. vii, p. 50, pi. iii, figs. 34-39. 



