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, il. t. 2. f. 24.) 



Mya pictorum. Linn. S. Nat. ? ; Sturm, Fauna, v\. 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.; Rossm. Icon. t. 3. 

 f. 71. a. b. ; Pfeiffer, i. t. 5. f. 9, 10. ; Leach, Si/n. 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. Camp. 107. t. 16. f. 30.— U. pon- 

 derosus. Bossm. 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. Bonn, 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 



