173 
Tereh^atulaplanosulcata, L. G. de Koniuck, 1843, Descr. Anim. Foss. Terr. Garb. Belg., 
p. 301, pi. 21, fig. 2. 
ActmOGOnclmspa7'adoxus,Mc,Coj, 1844, Synop. Foss. Ireland, p. 156, pi. 21, fig. G. 
Athyris 'planosulcata, 1844, p. 148. 
Atrypa? obhisa, Idem, 1844, ibid., p. 155, pi. 22, fig. 20. 
Spirigera P>lan0sulcata, A, d’Orbigny, 1850, Prod. Pal., I, p. 150. 
Athyris ,, 
Spirigera „ 
Terehratula „ 
Athyris paradoxa, 
planosulcata, 
parvirostris, 
planosulcata, 
J. Morris, 1854, Cat. Brit. Foss., p. 131. 
V. Semeuow, 1854, Ueber Foss, schles. Kolileukalkes, p. 21. 
De Keyserling, 1854, in Scbrenk’s Eeise Nordosteu Enrop. Euss- 
lands, I, p. 91. 
McCoy, 1855, Brit. Pal. Foss., p. 436. 
M. V. Griinewaldt, 1860, Mem. Acad. Imp. Sci. St. Petersbourg, 
II (7), p. 105. 
T. Davidson, 1859, Mon. Brit. Carb. Brach., p. 80, pi. 16, fig. 
2-13, 15. 
Idem, 1860, Mon. Carb. Brack. Scotland, p. 16, pi. 1, fig. 10, 11. 
Meek and Wortlien, 1860, Procs. Acad. Nat. Sci. Philadelphia, 
p. 451. 
L. G. de Koninck, 1872, Eech. Anim. Foss., II, p. 54. 
This is a sublenticular shell, with slightly convex valves of nearly 
equal depth, sometimes slightly inflected or depressed at the base. The beak 
of the ventral valve is small, rather pointed, incurved, and pierced by a small 
foramen, not always very distinct, and placed at the edge of the opposite valve. 
The surface of both valves is ornamented with numerous parallel concentric 
lamelliform expansions, each of which is flat and longitudinally striated. 
'The spiral supports, consisting of twelve or fifteen spiral turns, fill the greater 
part of the interior of the shell. The muscular impressions are very small, 
and faintly marked. 
Dimensions. — The best preserved specimen sent me is only eleven 
millimetres long and ten broad, with a thickness of about four millimetres. 
Relations and Differences. — In explanation of the list of syno- 
nyms given above, I must state that Mr. McCoy has not only described this 
species under three different names, but has placed it in three distinct genera, 
according as his specimens exhibited more or less well-preserved traces of the 
