902 DR F. E. 0. REED ON THE 



it with this species or with Lept. rliomboidalis, with which fragmentary specimens 

 mioht be confused. 



Horizon. — Drummuck Group (Starfish Bed). 



Locality. — Thraive Glen. 



Genus Christiania, Hall and Clarke. 

 Christiania tenuicincta (M'Coy). 

 (Plate XVIII, fig. 19.) 

 1846. Produda tenuicincta, M'Coy, Syn. Silur. Foss. Ireland, p. 25, pi. iii, fig. 4. 

 1852. Leptnena tenuicincta, M'Coy, Syn. Brit. Pal. Foss. Woodw. Mus., p. 239, pi. m, fig. 40. 

 1870. Leplxna tenuicincta, M'Coy, Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 326, pi. xlvii, 



fig. 7-18. 

 1883. Leptsena tenuicincta, M'Coy, Davidson, ibid., vol. v, Silur. Suppl., p. 168, pi. xi, fig.' 28; pi. xii, 

 figs. 17-21. 



Davidson's figures and description of this species give a good idea of its external 

 and internal characters, but he omitted to mention the presence of the foramen in 

 the beak of the pedicle-valve. 



This foramen is frequently well seen in the specimens from Balclatchie with the 

 shell preserved, and even in internal casts the little projecting peg is seen in the 

 cast of the beak indicating its presence. It should also be mentioned that the whole 

 interior of the shell is sometimes ornamented with rather coarse longitudinal striae, 

 broken up in places near the margins into elongated pustules. 



The Craighead shells are narrower and longer than the others, widening anteriorly, 

 and are usually bilobed by a shallow rounded continuous depression extending from 

 the beak to the anterior margin of the pedicle-valve ; the ears are also more depressed 

 and more sharply marked off from the body of the shell. I am doubtful if all the 

 Girvan shells from different horizons belong to the same species, and the Craighead 

 form may at any rate be regarded as a variety for which the designation bilobata is 

 suggested. Hall and Clarke * referred the species to their genus Christiania. 



Horizons. — (l) Stinchar Limestone Group; (2) Balclatchie Group; (3) White- 

 house Group ; (4) Drummuck Group. 



Localities. — (l) Craighead; (2) Balclatchie, Ardmillan ; (3) Shalloch Mill; (4) 

 Thraive Glen. 



Genus Strophomena, Blainville (sens, restr.). 

 Strophomena antiquata (Sowerby), var. nov. ivoodlandensis. 

 (Plate XVIII, figs. 20, 21 ; Plate XIX, figs. 1-5.) 

 ? 1870. Strophomena antiquata (Sowerby), Davidson (pars), Mon. Brit. Foss. Brack., vol. iii, pt. vii, 

 p. 299, pi. xliv, fig. 5 (non cet.). 

 1883. Strophomena antiquata (Sowerby), Davidson (pars), ibid., vol. v, Silur. Suppl., p. 193, pi. xv, 

 figs. 12-14. 



Shell subtriangular to semioval, rather wider than long, widest along hinge-linfe, 

 more or less produced anteriorly into a tongue-like fold or bluntly pointed, will) 



* Hall and Clarke, op. dt., Brach., i, p. 300. 



