262 NEW UNIONID^, MELANID^, ETC., 



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

 prominent; ligament short, thick and dark brown; epidermis olivaceous, inclining to 

 yellow, covered with interrupted rays which produce elongated subquadrate spots,, 

 with rather distant marks of growth; umbonial slope raised and rounded; posterior 

 slope narrow elliptical, subcarinate and slightly impressed ; cardinal teeth small^ 

 compressed conical and crenulate; lateral teeth long, thick, somewhat curved and 

 corrugate ; anterior cicatrices distinct, rather small and well impressed ; posterior 

 cicatrices confluent, large and moderately well impressed ; dorsal cicatrices placed in 

 the centre of the cavity of the beaks ; cavity of the shell very shallow ; cavity of the 

 beaks very shallow and obtusely angular ; nacre silvery white and iridescent. 



Remarks. — I have seven specimens of this species from Dr. Edgar and Mr. Pybas y 

 a single specimen from Dr. Edgar a long time since. It is very nearly allied to 

 Linchleyi (nobis), but is a smaller species, not so bright in the epidermis, nor are the 

 spots so distant and square. Pimciatus is thicker, more lenticular, and has smaller 

 cardinal teeth. It belongs to that group of which interruptus (nobis) may be 

 considered the type. None of the specimens had beaks perfect enough to designate 

 the kind of undulations of the tips, but the whole group seem to be very much alike 

 in this respect. 



Unio parous, pi. 33, fig. 77. 



Testa Irevi, late elliptica, subinflata, valde inrequilaterali, postiee subrotundata, antice rotunda ;, 

 valvulis subtenuibus, antice aliquanto crassioribus ; natibus prominulis, ad apices divaricate 

 undulatis ; epidermide polita, tenebroso-oliva, eradiata ; dentibus cardinalibus parviusculis^ 

 obliquis lamellatisque ; lateralibus longis, lamellatis subrectisque ; margarita cseruleo-alba et 

 iridescente. 



Shell smooth, widely elliptical, rather inflated, very inequilateral, rounded behind 

 and round before; valves rather thin, somewhat thicker before; beaks a little 

 prominent, with divergent folds at the tips: epidermis polished, dark olive, without 

 rays ; cardinal teeth rather small, oblique and lamellar; lateral teeth long, lamellar 

 and nearly straight ; nacre bluish-white and iridescent, 

 Proc. Acad. Nat. Sci. 1866, p. 34. 



Hah. — South America, Don Patricio M. Paz. 



My cabinet and cabinet of Don P. M. Paz. 

 Diam. -5, Length -7, Breadth 1*4 inch. 



Shell smooth, widely elliptical, rather inflated, very inequilateral, rounded behind 

 and round before ; substance of the shell rather thin, somewhat thicker before ;, 

 beaks a little prominent, with divergent folds at the tips; ligament thin and light 

 brown ; epidermis polished, dark olive, without rays, with distant marks of growth ; um- 

 bonial slope rounded ; posterior slope narrow, rather depressed, roughish ; cardinal teeth 



