1896.] NATURAL SCIENCES OF PHILADELPHIA. 563 



smooth in the middle, finely, irregularly striate at the ends and 

 basal margin. Green, duskier above, with narrow, widely spaced 

 and inconspicuous blackish rays, the eroded beaks deep purple. 

 Interior deep purple, clouded with whitish purple within the pallial 

 line, the teeth of the same light tint. Pallial line with a short triangu- 

 lar sinus ; right valve with three divergent cardinal teeth, median and 

 posterior teeth bifid at tip ; median tooth wide, anterior and poste- 

 rior teeth long and oblique ; left valve with three cardinals, the 

 median bifid at tip. Laterals crenulated, long, the anterior slightly 

 curved, posterior straight ; double in right, single in left valve. 



Length 32*, alt. 27J, diam. 15i mm. 



Length 28, alt. 24, diam. 15 mm. 



La Plata River above Colonia, Uruguay (Dr. Rush). 



Larger and more triangular than C. limosa. The lateral teeth 

 are unusually long, and the cardinals widely divergent. 



MUTELID^. 



Glabaris latomarginatus Lea var. felix n. r. PI. XXVI, fig. 8. 



Similar in form to Anodonta latomarginata Lea, but epidermis 

 light yellowish-green, closely painted with short radiating dichoto- 

 mous or simple lines or narrow V's of green, and two green rays on 

 the posterior slope. Interior pale pink within pallial line, prismatic 

 border faint olive buflf". Some black zig-zags along pallial line or 

 outlining muscle impressions. 



Length 53, alt. 38, diam. 20 J mm. 



Length 49, alt. 35, diam. 18 mm. 



Colonia, Uruguay (Dr. Rush). 



Glabaris trapesialis var. cygneiformis n. v. PI. XXVI, figs. 4, 5. 



Shell similar to some forms of Anodonta eygnea, such as that fig- 

 ured by Rossmiissler, Iconogr., I, fig. 280, in the elongate form, long 

 and up-curved posterior end, but hinge-line straight and produced in 

 a small wing anteriorly, terminating angularly. Very thin and 

 fragile, even in specimens 14 cm. long. Green and smooth in mid- 

 dle, blackish and roughened at ends and basal margin ; nacre blue- 

 white, iridescent, dark-stained in the cavity more or less, and often 

 with some zig-zag blackish markings around the muscles. 



Length 142, alt. 75, diam. 36 cm. ; alt. 52-53 %, diam. 26 % of 

 length. 



More compressed than G. riograndensis Iher., with the hinge-line 

 more angular at the ends and the posterior end peculiarly up- 



37 



