Species of Shells from Uruguay. 321 



nearly in a line with the front dorsal slope. Length 9 millims., 

 diam. 12, thickness 7. 



Hob. 36° 47' S. lat., 55° 17' W. long., 28 fms. Off the 

 estuary of the Rio de la Plata, Uruguay. 



This species is not unlike N. obliqua, Lamarck, as figured in 

 Hanley's monograph in Sowerby's 'Thesaurus Conch.' fig. 150. 

 It is, however, much more ventricose, has more of an angle at 

 the anterior end, and the inner margin is not minutely crenu- 

 lated. The teeth are remarkable on account of their length 

 and sharpness. There are three specimens of different sizes 

 from the above locality. The largest is of a brownish-olive 

 colour, the intermediate one greenish olive, and the smallest of 

 a still lighter tint. 



Corbula Tryoni. 



Shell a little inequilateral, small, very inequivalve, dirty 

 white, sharply rounded behind, scarcely beaked, and rather 

 squarely truncated anteriorly. Upper or smaller valve smooth 

 near the beaks, then exhibiting three or four strong concentric 

 ridges or stages of growth, which do not continue beyond a 

 slight angle running from the apex to the anterior ventral 

 extremity, the shell thus far, with the exception of that 

 portion close to the apex, being very finely radiately striated 

 and destitute of epidermis. Beyond this point the rest of 

 the surface (about half the diameter of the valve) is clothed 

 with a finely wrinkled epidermis. Lower valve also smooth 

 in the umbonal region, then closely and strongly ribbed, the 

 ribs becoming very fine, or almost disappearing, on a somewhat 

 raised rounded arcuate ridge from the apex to the anterior 

 ventral end. This prominence or ridge has a faint depression 

 on each side. Teeth one in each valve, that of the lower the 

 larger. Diam. 6^ millims., length 5, thickness 4. 



Hab. 32° 45' S. lat., 50° 39' W. long., 48 fms. East of 

 Uruguay. 



This, so far as I can ascertain, is the first record of a Corbula 

 from the eastern side of South America. I have much plea- 

 sure in naming this interesting species after Mr. Tryon, who has 

 given, in the ' American Journal of Conchology/ a valuable 

 catalogue of this genus. 



Crassatella uruguayensis. 



Shell compressed, subquadrate; anterior side broad, squarish, 

 margin but very little curved ; posterior end narrowing and 

 rounded. Dorsal lines on each side of the umbones forming 

 an angle of about fifty degrees. Hinder slope rather sudden, 

 a trifle concave, anterior rather longer and a little curved out- 

 wardly. Ventral margin arcuate, but only slightly so. Sculp- 

 ture consisting of concentric furrows and intermediate ridges, 

 coarsest at the centre of the valves and towards the apex, and 

 stopping short at the lunule and anterior dorsal area, both of 



