ATHYRIS. 147 



show sufficient character to enable us to judge whether they are the young of 

 some larger species, or one of those small Brachiopocls which cannot be satis- 

 factorily identified without some knowledge of their internal structure. 



Sub-genus — Seminula, M'Goy, 1844 ; emend., Hall and Clarke, 1894. 



2. Athyris (Seminula) oblonga, Sowerby, sp. Plate XVII, figs. 11. 11 a, 12 ? 12 a. 



1840. Atbtpa oblonga, Sowerby. Geol. Trans., ser. 2, vol. v, pt. 3, pi. liii> 



fig. G. 

 ? 1840. — indentata, Sowerby. Ibid., pi. liv, fig. 6. 



1864. Athyris ?, Davidson. Brit. Foss. Brach., vol. iii, p. 17, pi. iii, figs. 1, 16. 

 1896. Atuyris ? oblonga, Whidborne. Proc. G-eol. Assoc, vol. xiv, p. 375. 



Description. — Shell slightly pentahedral (or suborbicular), subglobose. Ventral 

 valve the larger ; beak prominent, with short dental lamellae ; muscle-scars appa- 

 rently very short and wide. Dorsal valve with very small dental sockets ; muscle- 

 scars short, cylindrical, and very narrow ; hinge-plate broad, anteriorly straight. 

 Cast of both valves covered with vascular impressions. Fold and sinus apparently 

 only marginal, low, and not very broad. Surface quite smooth, but with four or 

 five growth-ridges. Margins meeting in an arching line, the ventral valve being 

 thrown back at the shoulders and then advancing to the front. 



Size. — Length 19 mm., width 19 mm., depth 10 mm. 



Localities. — Ashford Strand, Laticosta Cave Baggy, Saunton, Poleshill, 

 Roborough, &c. 



Remarks. — An internal cast with a portion of the mould of the same shell is 

 in my Collection, and from this specimen the above description has been almost 

 entirely taken. Judging from Hall and Clarke's revision of the Athyridse this shell 

 clearly falls within the limits of the sub-genus Seminula of M'Coy, 1 of which they 2 

 say that its smooth exterior, its subpentahedral form, its sinuate valves, and the 

 peculiar character of its muscle-scars are distinctive features, and that branching 

 vascular sinuses are sometimes retained over the whole pallial area of both valves. 

 In our specimen all these points are observable, though its fold and sinus are very 

 indistinct. Similar specimens seem not uncommon at Ashford, and a bed close to 

 the Laticosta bed at Baggy is paved with valves, which from their shape and 

 smoothness (excepting their few growth-lines) are undoubtedly identical. I have 



1 1844, M'Coy, 'Synopsis Carb. Foss. Ireland,' p. 158. 



2 1894, Hall and Clarke, ' Pal. N. T.,' vol. viii, pt. 2, p. 93. 



