'292 DESCRIPTION OF NEW 



number of minute impressions may be observed in both valves, posterior to the anterior 

 cicatrix. Whether these are muscular attachments or not I am not certain ; older and 

 thicker specimens would enable one to judge. It has the triangular fosset common to 

 the South American species. The margin is broad for the size of the shell, and the 

 granules of it are very perceptible with a microscope of good power. 



This species comes so near in its characters to the An. crispata, my specimen of which 

 came from Cayenne, that it is with some hesitation that I have separated it. The tortilis 

 has the festooned crimples much finer, and they do not extend over the whole disk, 

 as in the crispata, nor are they by any means so much impressed, but change into stria? 

 on the posterior slope and on the anterior portion of the disk. The tortilis is also rather 

 longer and more compressed towards the beaks. On the crispata the festooned crimples 

 are much coarser, and the marks of growth are different. Dr. Gould, in the Proceedings 

 of the Boston Society of Natural History, November, 1850, described an Anodonla, under 

 the name of g/cmca, brought by the Exploring Expedition, which I believed at the time to 

 be the crispata-, Lam. The specimen seemed to me to be of the same species with that 

 which I procured from Ferussac, in Paris, under the name of crispata. The name of 

 glauca also is preoccupied by Valencienes, for another Anodonta from South America. It 

 is with some hesitation I place this in the division of "plicate" species, as it almost 

 requires a lens to see the folds, but it cannot be called a " smooth" shell. 



Anodonta Schroteriana. PI. XXIX. Fig. 55. 



Testa tsevi, transversa, subcompressa, valde insequilateraM, postice obtuso-biangidari ; vatvulis subcrassis; 

 natibus prominent ibus, acutis; epidermide rugosd, crebrissime striata, tencbroso-olivd, obsolete radidtd; 

 margaritd alba et iridesccnte. 



Shell smooth, transverse, rather compressed, very inequilateral, obtusely angular behind ; valves rather thick; 

 beaks prominent and pointed; epidermis rough, thickly striated, dark-olive, indistinctly radiated ; nacre white 

 and iridescent. 



Hab. Rio Negro, Brazil, Mr. C. M. Wheatley. 



My cabinet and cabinet of Mr. Wheatley. 

 Diam. .9, Length 1.5, Breadth, 3.1 inches. 



Shell smooth, transverse, rather compressed, very inequilateral, obtusely biangular 

 behind, slightly compressed on the sides near the middle of the dorsal line, with a slight 

 callus under the beaks; substance of the shell rather thick; beaks prominent, pointed and 

 placed towards the anterior margin; ligament long and rather thin; epidermis very rough, 

 covered with very close crimplcd strife, dark-olive, with a few indistinct rays over the 

 posterior slope, and with rather distant lines of growth; posterior slope long, compressed 

 into a carina; umbonial slope slightly raised and rounded; anterior cicatrices distinct, the 

 smaller one very minute; posterior cicatrices confluent; no visible dorsal cicatrices; pal- 

 leal cicatrices slightly impressed ; cavity of the shell rather shallow and wide ; cavity of 

 the beaks shallow and angular; nacre with minute striae from the beaks towards the mar- 

 gin, white and iridescent. 



Remarks. — A single specimen, or rather the two valves of different individuals, was 

 kindly given to me by Mr. Wheatley. It docs not seem to have been noticed by Spix or 



