292 NEW UNIONID^, MELANID^, ETC., 



Remarlis. — This species of Anodonta was among the shells taken by Mr. Bridges, 

 in Nicaragua. Like the other Unionidce brought to this country by some col- 

 lectors from California, there remains a possibility of error in the habitat. Un- 

 fortunately this industrious botanist did not live to bring his collections home, and 

 the Unionidai were sent to San Francisco and there distributed as coming from Lake 

 Nicaragua. Several known species of this collection inhabit Lake Nicaragua, but 

 there are two species of Micetopus which heretofore have only been found in South 

 America. This fact, and this only, throws some doubt as to the exact habitat of 

 the species of Unionidce, which have not before been observed. All the UnioitBs 

 received have that peculiar sulcation over the whole disk which characterise all the 

 sjjecies I have seen from Lake Nicaragua; and they are by no means rare in our 

 cabinets. But heretofore I have not seen an Anodonta from this Lake, while in this 

 collection there are several. All this doubt must be taken into consideration as to 

 the habitat of the species described in this paper said to have come from Lake 

 Nicaragua. The species above described is somewhat like trapezialis, Lam., but 

 differs in being more rectangular and having the dorsal and basal lines nearly 

 parallel. There is a disposition in all the specimens before me to be slightly com- 

 pressed in the middle, from the beaks to the base, which causes a slight arcuation 

 on the basal margin, and on this space there is usually a broad line of slightly 

 darker color. The posterior slope is of a dark green color. The nacre is of most 

 extraordinary brilliancy, radiant with all the colors of the sjaectrum, being opalescent 

 over the whole interior. I have peculiar gratification in dedicating this fine species 

 to the memory of the distinguished botanist, who, after many years of successful 

 examination of tropical vegetation, was unfortunately unable to return to his family, 

 having died at sea of tropical fever, on his way from Panama to San Francisco. 

 His friend. Dr. Hooker, has honored him by naming a genus of plants after him, 

 calling it Bridgesia. 



Anodonta injequivalva. PI. 43, fig. 108. 



Testa Itevi, obovata, compressa, incequivalva, iiisequilaterali, antice et postice rotundata ; valvulis 

 subtenuibus ; natibus subprorainentibus ; epidermide vel teuebroso-viridi vel luteo-vi-ridi, obsolete 

 radiata ; margarita ca;ruleo-alba et valde iridescente. 



Shell smooth, obovate, compressed, inequivalve, inequilateral, rounded before and 

 behind ; vfilves rather thin ; beaks somewhat prominent ; epidermis dark green or 

 yellowish-green and obscurely radiated ; nacre bluish-white and very iridescent. 

 Proc. Acad. Nat. Sci. 1868, p. 95. 



Eab. — Lake Nicaragua, Central America, Mr. W. M. Gabb. 



My cabinet and cabinet of Academy of Natural Sciences. 

 Diam. -7, Length l-l, Breadth 1'6 inch. 



