UNIO. 279 



a. Anterior teeth compressed, elevated, sometimes 

 crested. 



129. 1. UNIO pictorum. Thin Painters' Union. 



Shell oval-oblong, ventricose, produced into 

 a bluntly truncated beak behind, yellowish 

 green, brownish zoned, greenish behind; 

 upper edge nearly straight, lower rather 

 retuse; hinge teeth very much compressed, 

 arched, crenated ; hinder teeth of left valve 

 small or evanescent, (t. 2. f. 11.) 

 Young shell with a few isolated conical tubercles 

 on the umbo. (Pfeiffer, ii. t. 2. f. 24.) 



Mya pictorum. Linn. S. Nat. ? ; Sturm, Fauna, vi. 2. f. a. ; 

 Wood, Conch. 104. t. 19. f. 3, 4. Schroet. Flussc. t. 4. 

 f. 6. Unio pictorum. Lam. Hist. vi. 77.; Ency. Meth. 

 t. 248. f. 4. ; Drop. Moll. t. 11. f. 4.; Eossm. Icon. t. 3. 

 f. 71. a. b. ; Pfeiffer, i. t. 5. f. 9, 10. ; Leach, Syn. Moll. 

 32. a. ; Forbes and Hanley, B. M. ii. 142. t. 39. f. 1., 

 t. 2. f. 2. Unio rostratus. Pfeiffer, i. 114. t. 5. f. 8.; 

 Alder, Mag. Nat. Hist. ii. Mysca pictorum. Turton Bi- 

 valves, 245., Man. ed. 1. f. 11. Unio elongatula. Pfeiffer, 

 ii. 35. t. 8. f. 5, 6. Unio limosus. Nilson, Moll. Suec. 110. 

 U. Deshayesii. Mich. Comp. 107. t. 16. f. 30. U. pon- 

 derosus. Rossm. Icon. xii. 31. f. 767 U. longirostris. Rossm. 

 Icon. xi. 13. f. 738. U. Philippi. Dup. Cat. 209., Hist. 

 M. F. t. 28. f. 19. U. curvirostris. Normand.; Ross. Icon. 

 f. 200. Mya ovalis. Donn, B. S. iv. 89. 



The old shell becomes much thicker ; and some of 

 the varieties, as that called U. Philippi, almost form 

 a passage to U. tumidus. 



b. Anterior teeth conical, high. 



130. 2. UNIO tumidus. Tumid Union. Shell ovate 



elongate, wedge-shaped, tumid, produced and 

 attenuated behind, thick, brown ; lower edge 



T 4 



