EXOTIC UXIOXID/K. ... 



young have a well-defined anterior lamellar tooth and a distinct posterior raised lino, 

 which, in the left valve, is slightly divided. This is so marked in these young 

 specimens, that one would hardly hesitate to place them among the Uniones if we had 

 not the adults, which have scarcely a vestige of the elevated lines on the dorsal 

 margin. 



Unio Sumatrensis. pi. 34, fig. 118. 



Testa plicatfi, .subtriangulari, subventricosa, posticc subbiangulata, injequilaterali ; valvulis .subcrassis ; 



natibus subprominentibus; cpidermide micante, lutco-oliva, postice vireiiti ; dentibus cardinalibus 



lamellatis, conipressis, obliquis, in utroquo valvulo duplicibus : lateralibns subbrevibiis curvisquc ; 



margarita alba et iridescoiite. 



Shell plicate, subtriangular, rather inflated, snbbiangular behind, inequilateral; 



valves rather thick ; beaks somewhat prominent ; epidermis shining, yellowish olive, 



greenish behind ; cardinal teeth lamellar, compressed, oblique and double in Iwth 



valves ; lateral teeth rather short and curved ; nacre white and iridescent. 



r»w Sumntrcims,l,CTi. Prnr. Acad. Nat. Sfi., 1S.',9, p. 1:i3. 



JJah. — Sumatra. H. Cuming. 



My cabinet and cabinets of Mr. Cuming and C. M. Wheatley. 

 Diam. -9, Length 1-1, Breadth 18 inches. 



Shell • with very small folds nearly over the whole disk, subtriangular, rather 

 inflated, subbiangular behind, inequilateral; substance of the shell rather thick; 

 beaks somewhat prominent ; ligament short, thin and bright brown ; epidermis shining, 

 yellowish olive, subsulcate, without rays ; umbonial slope raided and rounded ; pos- 

 terior slope wide, with very small oblique, nearly parallel folds; cardinal teeth 

 lamellar, compressed, very oblique, nearly straight and double in both valves ; lateral 

 teeth rather short and curved ; anterior cicatrices confluent ; posterior cicatrices con- 

 fluent ; dorsal cicatrices placed on the under side of the posterior portion of the 

 cardinal teeth ; cavity of the shell deep and rounded ; cavity of the beaks rather 

 deep and obtusely angular ; nacre white and iride.sceut. 



Remarlcs.— In outline and color this species is allied to V. Javanm (nobis), but it 

 is more triangular, more inflated and has small irregular folds over the whole disk. 

 It is greatly to be regretted to be obliged to make diagncses from single specimens as is 

 necessary in many of these rare foreign species. When many and more perfect 

 specimens are obtained very essentially difteront characters may be observed. 



Anodonta gracilis, pi. 34, fig. 119. 



Testa Isevi, transver.sa. subcylindracea, valde inaequilaterali ; valvulis tenuibus; natibus subproniii.entibus, 

 ad apices undulatis : cpidermide flavescente, striata; mari^arita vel alba vcl pcrpurea ot valde 

 iridcseente. 

 Shell smooth, transverse, sul)cyliHdrical, very inequilatenil ; valvi-s thin : beaks a 



