30 UESCRIPTIONS UF 



slope and Hattened on the side ; beaks a little prominent, with rather short divergent 

 and re-entering ribs at the apex ; liganrent short and thin ; epidermis yellowish olive, 

 minutely striate, apparently without rays ; umbonial slope subanguldr ; posterior slope 

 raised nearly into a wing ; cardinal teeth small, compressed, crenulate, oblique and 

 double in both valves ; lateral teeth long, lamellar, single in the right and double in the 

 left valve ; anterior cicatrices confluent ; posterior cicatrices confluent ; dorsal cicatrices 

 placed in the centre of the cavity of the beaks ; cavity of the shell rather deep and 

 rounded ; cavity of the beaks rather shallow and angular ; nacre bluish white and 

 very iridescent. 



Remarks. — Among a number of interesting land and fresh water shells which I 

 procured from Mr. E. Verreaux, in Paris, was a single small specimen of this 

 species, evidently quite young. I should suppose about one-fourth grown. The above 

 diagnosis therefore may be found to be, in many respects incorrect, when mature 

 individuals shall be examined. The oblong outline of this shell is remarkably regular. 

 The costse of the beaks are smaller on the posterior and anterior slopes and several of 

 them form re-entering angles on the posterior slope and on the sides. This species has 

 some affinity to Glvarrvmixis, D'Orb., but differs in being more oblong, in having 

 smaller costae on the beaks, and in having the posterior slope more elevated. 



Unio Nuttallianus. pi. 30, fig. 25. 



Testa laevi, elliptica, subinflata, inaequilaterali ; valvulis tenuibus ; natibus prominulis ; epidermide olivaceii, 

 eradiata, valde polita ; dentibus cardinalibus parvis, rectis, compressis crenulatisque ; lateralibus sub- 

 curtis, subrectis lamellatisque ; margaritfl, salmonis colore tincta et iridesoente. 

 Shell smooth, elliptical, rather inflated, inequilateral ; valves thin ; beaks slightly 



prominent ; epidermis olive, without rays and much polished ; cardinal teeth small, 



straight, compressed and crenulate ; lateral teeth rather short, nearly straight and 



lamellar ; nacre salmon color and iridescent. 



Proc. Acad. Nat. Sci. Vol. 8, p. 103. 



5a&.— India. Prof. Thomas Nuttall. 



My cabinet and cabinet of Prof Nuttall. 

 Diam. -6, Length -8, Breadth 1.3 inch. 



Shell smooth, elliptical, rather inflated, inequilateral, subangular behind, rounded 

 before ; substance of the shell rather thin, thicker before ; beaks slightly prominent ; 

 epidermis olive, without rays, highly polished and with transverse yellow bands ; 

 ligament short and very thin ; umbonial slope obtusely angular ; posterior slope rather 

 flattened ; cardinal teeth small, straight, compressed, crenulate and double in both 

 valves ; lateral teeth rather short, nearly straight, lamellar, single in the right and 

 double in the left valve, the lower division being much larger and rising towards the 

 end into a crest ; anterior cicatrices distinct ; posterior cicatrices confluent ; dorsal 

 cicatrices placed within the cavity of the beaks, and under the plate ; pallial cicatrix 



