450 CARBONIFEROUS LAMELLIBRANCHIATA. 



CoNOCAKDiujr, Ilall, 1858. Trans. Albany lust., vol. iv, p. 15. 



— Eichwald, 1860. Lethiea Kossica, p. 1021. 

 Pleubohhynciius, Griffith, 18G0. Journ. Geol. Soc. Dublin, vol. ix, p. 91. 

 CoNOCAEDiuir, Wardle, 1802. In Sleigh's Ancient Hist. Leek, p. 285. 



— Winchell, 1862. Proc. Acad. Nat. Sci. Philadelphia, p. 420. 



— Meeh and Worthen, 1865. Ibid,, p. 249. 



— JDnwson, 1868-78. Acadian Geology, p. 304. 



— Young and Annstrong, 1871. Trans. Geol. Soc. Glasgow, vol. iii, 



p. 50. 



— StoUczkn, 1871. Pal. Indica, vol. iii, p. 211. 

 PLEURonnYNCHUs, Baily, 1871. Journ. Eoy. Geol. Soc. Ireliind, vol. iii, p. 25. 

 CoNOCARDiUM, R. Etlicridge, jun., 1873. Geol. Mag., vol. x, pi. xii, fig. 5, p. 297. 



— Meeh and Worlhen, 1875. Geol. Surv. Illinois, vol. vi, p. 529. 

 Pleueoehynciius, BaiJij, 1875. Figs. Char. Brit. Fossils, p. 115. 

 CoNOCAEDiUM, Armstrong, Young, and Robertson, 1876. Cat. W. Scott. I'oss., 



p. 53. 



— Rdmer, 1876. Lethaea Palseoz. Atlas, pi. xliv, fig. 4. 

 Pleueoriitnchus, Kinahan, 1878. Man. Geol. Ireland, pi. iii, face p. 63. 

 CoNoCAEDiuM, Btcjshy, 1878. Thesaurus Devonico-Carboniferus, p. 303. 



— Whitfield, 1882. Bull. Amer. Mus. Nat. Hist., vol. i, no. 3, p. 61. 



— Colletf, 1883. Twelfth Ann. Eep. Geol. Indiana, p. 347. 



— Hall, 1884. Nat. Hist. New York, Pal., vol. v, pt. 1, no. 2, 



p. xxxiv. 



— Waleott, 1884. U.S. Geol. Surv. Pal. Eureka Distr., p. 177. 



— de Koniuck, 1885. Ann. Mus. Hoy. Hist. Nat. Belg., vol. xi, 



p. 99. 



— R. Etheridge, 1888. Brit. Foss., pt. 1, Palaeozoic, p. 281. 



— Miller, 1889. N. Amer. Geol. and Palaeont., p. 472. 



— Worthen, 1890. Geol. Surv. Illinois, Pal., vol. viii, p. 112. 



— Whidborne, 1891. Monograph Devonian Fauna, vol. ii, pt. 1, 



p. 18. 



— Keyes, 1894. Missouri Geol. Surv., vol. v, p. 124. 



— Tornquist, 1896. Fossilfiihr. Untercarbon. Siidvogesen, p. 106; 



Abhandl. geol. Specialkarte Elsass-Lothringen, 

 vol. V, p. 640. 



Generic Characters. — Shell equivalve, very inequilateral, more or less fusiform 

 or triangular, rapidly compressed and truncated behind so as to form in the 

 majority of the species of the genus a posterior surface, which is cordiform and 

 often concave, bisected by a slight median ridge formed by the closed edges of the 

 valve, from the upper part of which springs the characteristic tubular rostrum. 

 The anterior end is triangular and produced, gradually narrowed and compressed, 

 consisting of the wing and lateral surface of the valve, gaping largely. The 

 anterior border is curved, forming a right angle with the hiuge-line; it descends 

 for a short distance and then rapidly curves backwards and downwards in a single 

 sweep or sinuous till it meets the postero-inferior angle of the dorsal surface. 



