20 DESCRIPTIONS OF 



lateral tooth in both valves. Like nucleus herein described the transverse close striae 

 are very remarkable, and in both, the folds are beautifully developed on the inside. 

 In some specimens the striae are nearly obliterated. 



Unio substriatus. pi. 26, fig. 14. 



Testa Isevi, elliptica, subinflata, subacquilaterali, postice angulata, anticC rotundata ; valvulis crassius- 

 culis ; natibus subprominentibus granulatisque ; epidermide oUvacea eradiata et rugoso-striata ; den- 

 tibus cardinalibus longis, rectis lamellatisque ; lateralibus longis, rectis lamellatisque ; margarita 

 argentea et iridescente. 

 Shell smooth, elliptical, subinfiated, nearly equilateral, angular behind, surrounded 

 before ; valves rather thick ; beaks a little prominent and granulated ; epidermis olive 

 colored, rayless and rugosely striate ; cardinal teeth long, straight and lamellar ; lateral 

 teeth long, straight and lamellar ; nacre silvery and iridescent. 

 Proc. Acad. Nat. Sci. Vol. 8, p. 93. 



iTaft.— Siam. S. R. House, M. D. 



My cabinet. Cabinet of W. A. Haines, New York. 

 Diam. -4. Length -5. Breadth 11 inch. 



Shell smooth, elliptical, somewhat inflated, nearly equilateral, angular behind and 

 rounded before ; slightly constricted from the beaks to the basal margin ; substance of 

 the shell rather thick ; beaks a little prominent, with a few small granules at the top ; 

 ligament rather long and thin ; epidermis olive colored, rayless, minutely and rugosely 

 striate ; posterior slope with two raised lines, and one impressed one nearest to the 

 margin ; umbonial slope rounded ; cardinal teeth long, straight and lamellar, double 

 in the right and single in the left valve ; lateral teeth long, straight and lamellar, 

 double in the left and single in the right valve; anterior cicatrices confluent ; posterior 

 cicatrices scarcely perceptible ; dorsal cicatrices imperceptible ; cavity of the shell 

 rather deep and rounded ; cavity of the beaks angular and shallow ; nacre silvery- 

 white and iridescent. 



Remarks. — Two opposed valves of nearly the same size were all which Mr. Haines 

 received among his Siamese shells. In form and general character this species is 

 nearly allied to U. inornatus herein described. It differs in being a little more 

 transverse, and in being thicker and smaller. It resembles in outline U. cceruleiw, 

 (nobis,) but has no bluish tint in the epidermis, and is entirely without rays, and is 

 smaller. It is a very small species, not larger than a middle sized U. parvus, Barnes. 

 It might be mistaken for a young U. Ingallsiamis, (nobis,) but that shell is more oblique 

 and smoother, and differs in the color of the postei'ior slope. 



Unio Africanus. PI. 27, fig. 15. 



Testa laevi, elliptica, subcompressa, subemarginata, valdo insequilaterali, postice obtuse angulata ; valvulis 

 subtcnuibus; natibus parvLs, pronjinulis undulatisquc ; epidcrniidr lutco-olivaccri el politA ; (Icutibus 



