192 NEW-YORK FAUNA — MOLLUSCA. 



proaches the rostrated extremity, when it becomes perceptibly concave. Ligament long, 

 elevated and prominent. Cardinal teeth small, oblique, compressed, tripartite, crenate ; 

 lateral teeth crenate on the edges. Surface smooth, occasionally concentrically squamous. 



Color. Epidermis greenish brown and brownish, approaching often to black ; beaks lighter : 

 within bluish white, iridescent, often salmon-colored. 



Vertical axis, 1 "4 ; transverse ditto, 3 "2. 



The specimen which furnished the above description was obtained from Wolcott creek, 

 Lake Ontario. It corresponds in the main with the description of my late friend Mr. Barnes, 

 but is much larger, more solid, and of a uniform deep salmon-color within. Dr. Newcomb 

 has, I understand, detected in the Champlain canal a variety ? of this species, with a single 

 tooth in the left valve. 



Unio rosaceus. 



PLATE XXXIX. FIGS. 355 (Adult) ; 356 (Young). — PLATE 40. FIG. 357 (Sexual variety). 

 (STATE COLLECTION.) 



Description. Shell moderately solid ; in the adult, rather inflated ; in the less mature 

 specimens, somewhat compressed ; regularly and shortly rounded at one extremity, broadly 

 rounded at the other, slightly alated above the hinge-margin, and in the adult this alation 

 obscurely plaited. Basal margin usually widely rounded : occasionally distinctly compressed 

 in the middle of the basal margin, by one or more impressed oblique lines, which are said 

 to be a sexual distinction (See fig. 356) : these lines are not apparent in the adult. Beaks 

 prominent, incurved, approximate, decorticated. Shell slightly gaping at the shorter extremity. 

 Surface lustrous, strongly impressed by the lines of growth. Cardinal teeth in one valve, 

 two ; the anterior small, obliquely directed forward ; the posterior large, triangular, erect, its 

 summit incurved upward ; lateral tooth distinct and broad : in the other valve, the cardinal 

 teeth are subequal, crenulated and separated by a deep pit, and are strengthened in both 

 valves by a strong rib beneath extending across the shell. Anterior muscular impression deep, 

 with a small oval depression behind it at the base of the rib above mentioned. 



Color. Yellowish brown ; in the younger specimens, with a faint greenish tinge at the 

 anterior extremity : within iridescent, rosaceous ; in the younger specimens, bluish white. 



Vertical axis, 1'5; transverse ditto, 2-5. Diameter, 0*8. 



Many specimens of this shell have been received from Dr. Sartwell, from Seneca lake (fig. 

 356 as the female, and 357 as the male shell). I find no description which coincides with the 

 characters of the above shell. It is undoubtedly allied to iV. cariosus and luteolus ; from the 

 latter, which it most resembles in form, it is readily distinguished by the cardinal teeth. 



