158 UNIONID^. 



variations. The glossy epidermis is usually of a light and 

 somewhat olivaceous yellow green, often changing into grey 

 or ash colour upon the umbones, and adorned with two or 

 three broad darker (often bluish-green) rays adjacent or 

 beyond the umbonal fold. These rays, we may remark, 

 are present in most of the varieties. The beaks and 

 umbones are scarcely raised above the dorsal line ; the 

 former are flattened and very indistinct ; the latter are 

 channelled with small concentric folds. The nacre is 

 silvery or occasionally of a pink or flesh-colour. The ob- 

 scure pliciform wrinkles, which are indicated upon its sur- 

 face, become more prominent features in Cellensis (Myt. 

 anatinus, Penn. Brit. Zool. ed. 4, vol. iv. p. 118, pi. 68, 

 f, 79. — Maton and Rack. Trans. Linn. Soc. vol. viii. pi. 8a. 

 f. 1. — Sheppard, Trans. Linn. Soc. vol. xiii. pi. 5, f. 5. — 

 Flem, Encycl. Edin. vol. vii. pi. 204, f. 4. — Myt. Zellensis, 

 GrMELiN, Syst. Nat. p. 3362, from Schroter, Fliissconch. 

 pi. 2, f. 1. — Anod. sulcata, Nilsson. Moll. Suecise Terr, et 

 Fluv. p. 118. — Anod. cygneus, Turt. Manual, (and Gray) 

 Land and Fresh W. Shells, pi. 1, f. 8. — Brown, 111. 

 Conch. G. B. pi. 28 (erroneously 27), f. 1. — Anod. Cellensis, 

 Pfeiffer, Deutsch. Land und Siissw. Moll. pt. 1, p. 110, 

 pi. 6, f. 1. — E-ossmassl. Iconog. Land und Siissw. Moll, 

 pt. 4, p. 22, pi. 19, f. 280), whose contour is still more 

 elongated, its valves more unequally and subumbonally 

 ventricose, its hinder end more beaked, its epidermis 

 of a greyer tint, its basal margin retuse, and its dorsal 

 line straight or slightly concave. In ventricosa {Anod. 

 ventricosa, Pfeiffer, Deutsch. Land und Siiss. Moll, 

 pt. 2, p. 80, pi. 3), the valves are solid and swollen, and 

 rather more oblique than in the two preceding varieties. 

 Its epidermis is olivaceous, its front extremity rather 

 attenuated below ; its hinder termination subrostrated : 



