856 DR F. R. C. REED ON THE 



Orthis (DalmaneUa) testudinaria, Dalman, var. 

 (Plate X, figs. 12-14.) 



Shell subcircular to transversely elliptical, plano-convex ; cardinal angles obtuse 

 or rounded. Pedicle-valve strongly convex, rounded, not carinate ; beak obtuse, 

 elevated, more or less swollen and incurved. Brachial valve flattened, with shallow 

 median indefinite depression widening anteriorly ; beak small, low, inconspicuous. 

 Surface of valves covered with numerous small ribs of rather unequal and irregular 

 size curving back on each side, the primaries usually rather stronger and giving off 

 one or two lateral smaller ribs or dividing into two equal or subequal ribs at 

 irregular distances, rarely increasing by intercalation. Shell substance densely 

 punctate. Interior of brachial valve with large oval muscular area about half the 

 length of valve, composed of two pairs of adductors, of which the anterior are the 

 smaller. 



Dimensions. — Length about 5-8 mm. 



Horizon. — Whitehouse Group. 



Localities. — Shalloch Mill, Whitehouse Bay. 



Remarks. — This small shell is rather imperfectly known, but it does not appear 

 to belong to the variety shallochensis, being more subcircular in form and having 

 the ribs coarser and less equal in size. It is too ill defined to warrant a distinctive 

 designation, but I do not think it can be referred to 0. argentea, His., which it was 

 labelled by Davidson, though this species is not recorded in his list of brachiopods 

 from the Girvan district. 



Orthis (DalmaneUa) cf. visbyensis, Lindstrom. 

 (Plate X, figs. 15, 16.) 



1883. Orthis turgida, M'Coy, Davidson (pars), Mon. Brit. Foss. Brack., vol. v, Silur. Suppl., pp. 187, 

 225. 

 Non 1868. Orthis turgida, M'Coy, Davidson, op. cit., vol. iii, pi. xxxii, fig. 18 (Penkill), non figs. 12-17, 19, 20. 



The specimens from Penwhapple Glen, measuring about 19 mm. long, which 

 Davidson erroneously referred to 0. turgida, M'Coy,* consist of two internal casts 

 of pedicle-valves with the shape, contour, and high incurved beak of 0. elegantnla 

 and 0. visbyensis, Lindstrom. The muscle-scar is deeply sunk, elongated, triangular, 

 well defined at sides but less so in front, where it is slightly emarginate, the median 

 adductor impression, which is fully one-third the width of the whole scar, being some- 

 what shorter than the diductors. The ribbing which is seen round the edge on the 

 fragments of shell attached to the casts consists of about 130-150 fine equal or sub- 

 equal rounded ribs separated by slightly wider interspaces and gently curved back 

 on each side. Similar specimens occur at Woodland Point, but no brachial valves 

 are known ; the ribs in the shells from this latter locality seem less equal in size and 



* M'Coy, Syn. Brit. Palxoz. Foss. Woodw. Mus., 1852, p. 229, pi. iH, figs. 20-24. 



