140 unionidte. 



U. TUMiDus, Retzius. 



Solid : umbones with confluent, concentrically disposed, angu- 

 lar wrinkles ; anterior teeth high and conical. 



Plate XL. fig. 1, 



Uniotumidus, Retzius, Nova Genera Test. p. 17. — Gray, Manual Land and 

 F. W. Shells, p. 297, pi. 2, f. 13. — Brown, 111. Conch. G. B. 

 p. 82, pi. 32, f. 5, 6, 7, 8. — Spengl. Skriv. Natiir. Selsk. 

 Kiobenh. vol. iii. pt. 1, p. 57. — Pfeiffer, Deutsch. Land imd 

 Siissw. Moll. pt. 2, p. 34, pi. 7, f. 2, 3, and pi. 8, f. 1, 2 ; pt. 2, 

 pi. 2, f. 25, (Young).— KiCKX, Moll. Brabant. Austral, p. 8.3.— 

 RosSMAS. Iconog. Land und Siissw. Moll. pt. 1, p. 117, pi. 3, 

 f. 70 ; pt. 2, p. 27, pi. 14, f. 202, 203, 204 ; pts. 7, 8, 

 p. 41, pi. 40, f. 542 ; pt. 12, p. 32, pi. 60, f. 772 to 778. — 

 Hanl. Recent Shells, vol. i. p. 205, pi. 2, Mya, f. 27. 

 Mya ovalis, Pulteney, Hutchins, Hist. Dorset, p. 27 (fide Mont.) — Mont. 

 Test. Brit. p. 34. 

 „ depressa, Donovan, Brit. Shells, vol. iii. pi. 101. 



„ ovata, Donovan, Brit. Shells, vol. iv. pi. 122. — Maton and Rackett, 

 Linn. Trans, vol. viii. p. 39. — Turt. Conch. Diet. p. 106. — 

 Wood, General Conch, p. 105, pi. 19, f. 5. — Dillwvn, Recent 

 Shells, vol. i. p. 50.— Index Testaceolog. pi. 2, Mya, f. 27. 

 Myiica „ Turt. Dithyra Brit. p. 246 ; Manual Land and F. W. Shells, 

 p.21,f. 12. 

 „ soKda, Turt. Dithyra Brit. p. 246, pi. 16, f. 2 ; Manual Land and F. W. 

 Shells, p. 22, f. 13. 

 Unio ovalis, Fleming, Brit. Anim. p. 416. — Brown, 111. Conch. G. B. p. 82, 

 pi. 31, f. 1, 2, 3, 4.— SowERBY, Genera Shells, Unio, f. 1.— 

 Reeve, Conch. Systemat. vol. i. pi. 87, f. 1. 



The principal difficulty in describing the Uniones^ is to 

 avoid laying that stress upon characters which, in most 

 other genera, would probably be held of specific value, but 

 here, from their extraordinary power of modifying both 

 contour and colouring, become of minor importance. In 

 this respect the present shell (at least in our native exam- 

 ples) does not vie with the succeeding : nevertheless, 

 briefer language than usual is requisite, that the characters 

 assigned to it may prove sufficiently broad and compre- 



