16 DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID.E. 



Unio pattinoides. pi. 4, fig. 12. 



Testa Isevi, obliqua, subcompressa, valde insequilaterali, antice rotundata, postice obtuse angulata ; 

 volvulis subcrassis, antice crassioribus ; iiatibus sabprominentibus, fere terminalibus; epidermide 

 luteo-brnnnea, maculata ; dentibus cardinalibus parvis, subcompressis sulcatisque ; lateralibus 

 longiusculis, subcompressis corrugatisque ; margarita argentea et iridescente. 



Shell smooth, oblique, somewhat compressed, very inequilateral, rounded before, 

 obtusely angular behind ; valves rather thick, thicker before ; beaks somewhat 

 prominent, nearly terminal ; epidermis yellowish-brown and maculate ; cardinal 

 teeth small, somewhat compressed and sulcate ; lateral teeth somewhat long, com- 

 pressed and corrugate ; nacre silver white and iridescent. 

 Proc. Adad. Nat. Sci., 1871, p. 193. 



Hal). — Clinch E,iver, Pres. Estabrook ; Holston River, Dr. Edgar and Miss Law. 



My cabinet, and cabinets of C. M. Wheatley and Dr. Lewis. 

 Diam. 1, Length 1-4, Breadth 1-8 inch. 



Shell smooth, oblique, somewhat compressed, very inequilateral, rounded before 

 and obtusely angular behind ; substance of the shell rather thick, thicker before ; 

 beaks rather prominent, nearly terminal; ligament rather short, thick and dark 

 brown; epidermis yellowish-brown, spotted with green interrupted rays, with rather 

 close marks of growth; umbonial slope slightly raised and rounded; posterior slope 

 narrow, cordate, occasionally with a few maculations; cardinal teeth small, some- 

 what compressed and sulcate; lateral teeth rather long, somewhat compressed and 

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

 cicatrices distinct, rather small and moderately impressed ; dorsal cicatrices placed 

 on the base of the cardinal teeth within the cavity of the shell ; cavity of the 

 shell wide and rounded; cavity of the beaks rather deep and angular; nacre silver 

 white and iridescent. 



Remarks. — 1 have had two old and worn specimens of this species for many 

 years, always unable to place them satisfactorily in any described species with 

 which I was acquainted, E-ecently Miss Law has sent several young and more 

 perfect specimens, and I no longer doubt of their being distinct. In outline it is 

 near to mundus and Lesleyi (nobis), but mundus has higher beaks, and both are 

 rather more oblique. None of these specimens have the beaks perfect enough to 

 show the undulations at the tips. 



