LEIOPTERIA THOMPSOXI. 17 



Hiirlet Limestone series, Bute; Garple Water, Wellwood, Muirkirk; Thornlie- 

 bank. 



Observations. — The type of Phillips's species is preserved in the Gilbertson 

 Collection of the Natural History Museum, South Kensington, and is refigured, 

 PI. I, fig. 9, l)y the kindness of the authorities. It is a characteristic species, 

 easily recognised by its surface ornament and shape, but in some species of />. 

 hmulata the ornament, though much closer, approaches that of the species under 

 discussion. 



A. gibbosa, M'Coy, PI. I, fig. 8, the type of which is preserved in the Gritfitli 

 Collection, Museum of Science and Art, Dublin, is a cast of tlic interior, l»ut tlie 

 characteristic surface is preserved on the posterior wing, and therefore this specific 

 name is regarded as a synonym. 



L. squamosa was not recognised by de Koninck as occui-ring in Belgium, and 

 does not appear to be very common in Great Britain. 



Letopteria THOMrsoxi, Portlod; sp., 1843. Plate III, figs. 10, 11 ; Plate IV, 



figs. 2, :3, 7, 12, 18. 



Pterinea Thompsoni, Partloch, 1843. Eei>. Geol. Loudonderry, p. 431, pi. xxv, 



fig. 10. 

 AvicTJLA Thompsoni, M'Coy, 1844. Synops. Carb. Foss. Iroland, p. 85. 

 ? Pterinea Thompsoni, Morris, 1854. Cat. Brit. Foss., 2ud edit., p. 181. 

 Gervillia laminosa, Wardle, 1863. Sleigh's Ancient Hist. Leek, pi. iii, fig. 4. 

 Leiopteria trigonalis, de Koninclc, 1885. Auu. Mus. Koy. d'Hist. Nat. Belg., 



torn, xi, p. 191, pi. XXX, fig. 11. 



— MODiOLARis, de Koninck, 1885. Ibid., p. 193, pi. xxx, fig. 7. 



— EMACiATA, de KoninrJ,-, 1885. Ibid., p. 195, pi. xxx, fig. 21. 

 Pterinea Thompsoni, Etheridge, 1888. Brit. Foss., pt. 1, PalfEozoic, p. 276. 



Sioecific Characters. — Shell below medium size, compressed, very inequilateral, 

 transversely triangular. The anterior end, comparatively long for the genus, 

 narrow, triangular, compressed, its extremity rounded, well marked off from the 

 body of the valve by the byssal sinus. The inferior margin descends downwards 

 and backwards, becoming well rounded behind, Avhere it curves upwards into the 

 posterior border, which is sinuous, convex below, somewhat concave aljovc. 

 The hinge-line is straight and long, sHghtly produced posteriorly. The umbones 

 are small and inconspicuous, hardly raised above the hinge-line, and situated 

 anteriorly. The body of the valve is obliquely and triangularly swollen, expanded, 

 and flattened behind and below, not well marked off from tlie gradually compressed, 

 elongate posterior wing. 



