8 PROCEEDINGS OF THE XATIOXAL MUSEUM. vol. 66 



valve the first cardinal tooth is a mere point, the second is strong, and 

 thick and weakly bifid, the third is modei'ately stout, long, and promi- 

 nently bifid — anterior laterals of this vahe short, the inner one very 

 thick and wavingly striated on its upper face, outer one weak, sharp, 

 its lower end abruptly curved to join the inner lateral, groove very 

 Avide and deep. In the left valve the first cardinal is triangular, high 

 and sharply pointed, the second is strong and so deeply bifid as to 

 appear like two teeth fused at the base, the third cardinal is long 

 and platelike. Anterior lateral of this valve thick with edge very 

 undulating and it and the upper face coarsely striated. Posterior 

 lateral of this valve thick with both its outer and inner faces coarsely 

 striated. Adductor scars, pallial line and sinus all deeply impressed. 



The type. Cat. No. 347874, U.S.N.M.. measures: Length, 21 mm.: 

 height, 20 mm.; diameter, 14 mm. It comes from the Department of 

 Colonia and was collected and presented by Doctor Felippone. 



Cat. No. 109265, U.S.N.M., contains two small specimens and four 

 odd valves from Arroyo de Pando, Department of Canelones, which 

 were received many years ago from Mr. S. Olea, of Montevideo. 

 Cat. No. 347876, U.S.N.M., contains a number of odd valves from 

 the Department of Paysanclti received from Doctor Felippone. Un- 

 like the type, many of them show several radiating lines of color. 

 These lines show on the calcareous portion of several specimens 

 which are almost entirely decorticated, and apparently it is in this 

 part of the shell that the color lines are located, showing through 

 the periostracum when it is present. 



The nearest relative of this species is C. fdipponei. which, however, 

 is much larger, more rounded, not so thick, and of different color. 



CORBICULA (CYANOCYCLAS) OLEAN'A. new species. 



Plate 1, figs. 2-4. 



Shell cordate, very oblique, very thick, much inflated, slopingly 

 rounded on posterior margin, angularly rounded on anterior margin. 

 Ventral margin regularly rounded. Beaks very high, projecting far 

 above the hinge line, which is much arched. Posterior ridge high, 

 rounded. Upper portion of shell with several very high, thin, con- 

 centric ridges, and whole surface with obscure concentric growth 

 striae. Posterior dorsal area with several obscure curved Kidiating 

 striae. Periostracum smooth, dull, unctttous, of a yellowish-olive 

 color, marked with a number of narrow radiating lavender-colored 

 lines. Area occupied by cardinal and lateral teeth, wide, thick, solid, 

 and strong. Cardinal teeth subparallel, fairly strong, all of them 

 bifid at the top. Laterals of right valve double, short, slightly bowed, 

 the inner ones moderately strong, the outer ones low and weak, the 

 iiTooves between the otiter and inner ones verv wide. Laterals of left 



