tribe nayades. 1/5 



Section B. — Non-Symphonote. 



* Plicated. 



U. NiCKLiNiANUs. Lea. Tr. Am. Ph. 5. t. \. Subtriangular, 

 inequilateral, very thick, oblique, very much spread out, with an 

 elevated wing, flattened towards the beaks, very much undulated 

 even to the point of the beak (except near the anterior and ventral 

 edges) ; cuticle dark brown, nacre pearly white ; teeth very thick, 

 the lateral curved. 5 . , 5-|. — China ? 



U. CcELATus. Conr. N. F. W. S. of Am. 7?. 29. t. 3, /. 4. 

 Subtriangular, very inequilateral, rough, much compressed, with a 

 broad furrow from the beaks to the base, (except the umbo and 

 posteriorly), covered with small irregular interrupted undulations 

 which ai'e profound behind the umbonal slope, with distant slight 

 concentric grooves ; umbones much flattened, beaks prominent ; 

 cuticle dark olive, obscurely rayed, nacre white and irridescent : 

 teeth thick. — Tennessee. 



U. Herds. Say. — U. Multiplicatus. Lea. on U. I. 

 p. 80. t. 4. f. 2. — U. Ligamentinus. (old) Lam? — Undu- 

 LATUS. Say. Am. Con. t. 16. Trapezoidal, inequivalve, trans- 

 verse, compressed ventrally and anteriorly, very thick, adorned 

 except posteriorly with broad undulations diverging from the um- 

 bonal slope, those near the carinated dorsal edge curving towards 

 it ; beaks slightly prominent, the umbones flattened : ligament 

 large long and curved ; cuticle black and much wrinkled, nacre 

 pearly white and irridescent : cardinal teeth thick, lateral long and 

 curved. 3^ . . 5f. — Ohio. 



U. Undulatus. Barnes, in Sil. J. 6. t. 2. f. 2. — U. Cos- 

 TATus. Co7i7'. Mon. U. t. 7. Rhombic- ovate, thick, with nume- 

 rous large waving oblique folds (except on the posterior side which 

 is very short obtusely rounded and merely marked by the transverse 

 wrinkles which become lamellar anteriorly) ; cuticle blackish 

 brown ; nacre pearly white, irregularly spotted mth brownish 

 green ventral edge little arcuated, not incurved : beaks not 

 pro'^xnent, eroded: cardinal teeth very thick, direct, sulcated. 

 32, .4|.— O/mo. 



U. Plicatus. Say. in Ency. Amer. — Barnes. ^' Hildr. in 

 Sil. J. — U. Peruviana. Lam. 4. — Raraplicata. Lam. 5. — 

 Dombeiana. Valen. in Humholdt. Voy. — U. Undulatus & 

 MuLTiPLiCATUS. Dcsli. Suboval, thick, ponderous, with two or 

 three more conspicuous undulations, which are profound very 

 oblique continued to the anterior ventral edge and not arising 

 from the decorticated umbo : nacre pearly. 



