68 ON THE NAIADES, 



Hab. River Parana, Province of Corrientes. Dr Burrough. 



My Cabinet. 



Cabinet of Dr Burrough. 



Cabinet of the Academy of Natural Sciences of Philadelphia. 



Diam. -1, Length 1-8, Breadth 2-4 inches. 



Shell subrotund, inequilateral, compressed, subangular behind, with 



large oblique folds on the beaks ; substance of the shell rather thick ; 



beaks somewhat elevated and distinctly plicate as far as the umbones ; 



ligament short and thin ; epidermis smooth, dark brown with transverse 



yellow marks of growth ; cardinal teeth large, elevated, lamelliform 



and double in both valves ; lateral teeth lamelliform and nearly straight ; 



anterior cicatrices and posterior cicatrices confluent ; dorsal cicatrices 



in the centre of the cavity of the beaks; cavity of the beaks subangular 



and shallow; nacre pearly white and iridescent. 



Remarks. — This is of the collection of Dr Burrough, sent by him 

 to the Academy of Natural Sciences of Philadelphia. To this gentle- 

 man natural science is much indebted for his unwearied industry in 

 contributing to the knowledge of the Fauna — of the numerous countries 

 through which he has travelled, in Asia, as well as on this continent. 

 This species resembles most, perhaps, the ladeolus (nobis), but differs 

 from it in being more round in the outline, in having longer and larger 

 folds on the beaks, and in being more compressed. In the beaks it 

 has some resemblance to the corriigatus (Lam.), as well also as in the 

 outline ; but the folds being nearly parallel to each other, it differs from 

 the corrugaius in these, which are usually zig zag in the latter shell. 

 I owe to the kindness of Dr Burrough the specimen in my cabinet, 

 and I have great pleasure in dedicating the species to him. 



Unio Sowerbianus. Plate X. fig. 28. 



Testci subtriangulari, inflatd, parte posticd peculiariter compressd et striatd ; 

 valvulis crassissiniis ; natibus valde prominentibus, dentibus cardinalibiis magnis ; 

 lateralibus crassis subrectisque ; margaritd in cavo albido-purpured. 



