78 ON THE NAIADES, 



them, the epidermis having been almost completely removed. What 

 remains indicates it to be greenish, and is sufficient to warrant its being 

 represented in the figure with a perfect epidermis — the ligament has 

 also been destroyed. I was informed by the dealer that it came from 

 Chili ; such authority cannot, however, be entirely relied on. The 

 cicatrices of this interesting species are very remarkable, particularly 

 that of the mantle near the margin ; the palleal impression is wide, 

 deeply impressed, and in the posterior part of the shell deflected towards 

 the centre of the cavity, somewhat similar to the excavation of the 

 palleal cicatrix of the genera Galathea and Madra. The character of 

 this cicatrix is different from that of any species of the family Naiades 

 I have seen, and this peculiarity induces me to believe that the animal, 

 when found, may prove to be different from that of the Anodonta. 

 Should this be the case, it will belong of course to a new genus, for 

 which I propose the name of Columba. It somewhat resembles the 

 An. exotica (Lam.). It is, however, narrower before and broader be- 

 hind than that shell. It gapes anteriorly and posteriorly more than 

 any of the Naiades with which I am acquainted. It is perhaps most 

 nearly allied to the Anodon crassus (Swainson), but differs in the dor- 

 sal line being straight, the nacre being pearly salmon, as well also in 

 the peculiar character of the palleal cicatrix. 



Anodonta tenebricosa. Plate XII. fig. 36. 



Tes/u ellipticd, transversa, insequilaterd, intus margine lata et corned; sinu 

 incurvo; valviclis crassis ; epidermicle tenebroso fusca ; margaritu alba subcseruled 

 purpura nubild, iridescente. 



Shell elliptical, transverse, inequilateral, interior with a broad horn coloured border; 

 sinus incurved ; valves thick ; epidermis dark brown ; nacre pearly white, clouded with 

 bluish purple, iridescent. 



Hab. River Parana, South America. Dr Burrough. 



My Cabinet. 



Cabinet of Dr Burrough. 



Cabinet of the Academy of Natural Sciences of Philadelphia. 



