386 NEW EXOTIC UNIONID-E. 



brown, minutely .striate and obscurely rayed ; cardinal teeth rather small, lamellar 

 and crenulate ; lateral teeth rather long, striate and curved ; nacre white and 

 iridescent. 



Hub. — Uruguay River, South America, Prof. J. Wyman. 



My Cabinet. 

 Diam. -5, Length 1-3, Breadth 1-5 inch. 



Shell smooth, subrotund, very much compressed, very inequilateral, rounded before 

 and behind ; substance of the shell somewhat thick, slightly thicker before ; beaks a 

 little prominent with divergent undulations ; ligament rather short, thin and light- 

 brown ; epidermis dark chestnut-brown, minutely striate, obscurely rayed and with 

 distant marks of growth ; umbonial slope very slightly raised and rounded ; posterior 

 slope narrow, raised into a well formed carina ; cardinal teeth rather small, lamellar, 

 striate, crenulate, and disposed to be much divided ; lateral teeth rather long, arched, 

 striate, curved and truncate at the end ; anterior cicatrices small, well impressed, con- 

 tinent with the lower and distinct from the upper ; posterior cicatrices confluent and 

 very indistinct ; dorsal cicatrices well impressed and placed in a row across the centre 

 of the cavity of the beaks ; cavity of the shell very shallow and very wide ; cavity of 

 the beaks shallow and rounded ; nacre white and iridescent. 



Bemarlis. — A single specimen only was brought by Prof. Wyman. It is probably 

 not full grown, being only about one and half inch in length and breadth, and bearing 

 the appearance of not being adult. The nacre is a rich white with the posterior 

 portion disposed to golden-yellow. It is nearly allied to Paranensis (nobis) in out- 

 line, but it is probably a much smaller species, is not inflated likethat species, nor 

 has it the polished epidermis. It also closely resembles in outline Fonlainiana, 

 D'Orb., and rotwndum, Spix, but it is more circular than either, and has a higher 

 carina on the posterior slope. The divergent undulations of the tips are small, and 

 do not extend to any distance. The epidermis is so finely striate that it has a satin- 

 like aspect. The striation is fuller near to the margin. 

 ■ 



Unio trifidtjs. PI. 44, fig. 295. 



Testa IjBvi, obliquo-oblonga, ad latere planulata, valde insequilaterali, postice acute angulata, antice ro- 

 tunda, ; valvulis crassiusculis, antice crassioribus ; nalibus prorninentibus, ad apices aspere et divari- 

 cate undulatis ; epidermide niicante, luteo-viridi, eradiata ; dentibus cardinalibus grandibus, trifidis, 

 sulcatis ; lateralibus longis, crermlatis, in valvulo dextro trifidis ; margarita argenteH et iridescente. 



Shell smooth, obliquely oblong, flattened at the side, very inequilateral, acutely 

 angular behind and round before ; valves rather thick, thicker before ; beaks promi- 

 nent, with divergent coarse undulations at the tips ; epidermis shining, yellowish- 

 green, eradiate ; cardinal teeth large, trifid, sulcate ; lateral teeth long, crenulate, 

 and trifid in the right valve ; nacre silver-white and iridescent. 



