ANIMALS. 189 



ScHizoDUS OBSCURUS, /. Sowerly . Plate XV, figs. 23, 24. 



AxiNUS OBSCURUS, J. Sow. Min. Conch., vol. iv, p. 12, pi. 314, upper figure, Dec. 1, 



1821. 

 (?) Cardium, N. S., Phillips. Phil. Mag., n. s., vol. iv, p. 401, 1828. 



AxiNUs OBSCURUS, J. Sow, Sedgwick, Trans. Geol. Soc. Lond., 2d series, vol. iii, p. 119, 



1829. 



— — „ De la Beche, Geol. Man., p. 384, 1831 ; Germ. Transl., 



p. 459, 1832; 3d Eng. ed., p. 573, 1833. 



— — „ Phillips, Encyc. Met., vol. iv, p. 616, pL iii, fig. 7, 1834. 



— — „ Thomson, Outlines Min. Geol. &c,, vol. ii, p. 310, 1836. 



— — „ Phillips, Lardner's Cycl., Geology, vol. i, p. 190, fig. 4, 



1837. 

 (?) — PARVUS, Brown. Trans. Manch. Geol. Soc, vol. i, p. 31, pi. vi, fig. 30, 1841. 



— (sp. unnamed). Brown. Op. cit., vol. i, pi. vi, fig. 18. 



(?) — UNDATUS ,, Op. cit., vol. i, p. 31, pi. vi, fig. 31. 



(?) — — „ Morris, Catalogue, p. 80, 1843. 



(?) — PARVUS „ Loc. cit. 



— OBSCURUS, J. Sowerby. Loc. cit. 



— — „ Brown, Fossil Conchology, pi. Ixxix, figs. 5, 6, 1843? 

 (?) — UNDATUS, Brown. Op. cit., pi. Ixxix, fig. 9. 



— (sp. unnamed). Brown. Op. cit., pi. Ixxix, fig. 7. 



— (ScHizoDUs) OBSCURUS, J. Sow. Be Verneuil, Bull. Soc. G6ol. de France, 2"" 



serie, vol. i, p. 31, 1844. 

 (?) — PARVUS, Brown. Loc. cit. 



(?) — UNDATUS „ Loc. cit. 



(?) — — „ Geol. Euss., vol. i, p. 224, 1845. 



(?) — PARVUS ,, Loc. cit. 



— OBSCURUS, J. Sow. Loc. cit. 



— — „ Philippi, Menke's Zeitschrift fiir Malakozoologie, p. 94, 



1845. 

 ScHizoDUS — „ Tennant, Strat. List., p. 88, 1847. 



— PARVUS „ Loc. cit. 



UNDATUS „ Loc. cit. 



Diagnosis. — " Obovate, posteriorly cuneiform ; anteriorly rounded ; surface convex, 

 with one obtuse keel ; beaks large." (Sowerby.^) 



This well-known species is characterised with thick valves, as shown by the 

 strongly-marked muscular impressions on casts (vide PI. XV, fig, 23) ; a somewhat 

 acuminated posterior end, caused by the ventral and dorsal margins sloping so much 

 towards each other ; a longitudinally-deep, rounded anterior end ; and posteriorly 

 twisted umbones. 



The fossils which Captain Brown has placed in the genus Awinus appear to me to 

 be referable to two species only, one of which I consider synonymous with Scldzodm 



^ Mineral Conchology, vol. iv, p. 12. 



