ART. 15 MOLLUSKS OF THE GENUS GORBICULA MAESHALL. 7 



straight, its edge creniilated and its upper face with several oblique 

 grooves, the outer tooth much arched. Anterior lateral of left rudely 

 crenulate and undulating, posterior lateral of this valve very high, 

 especially at its upper end, its edge finely crenulate and undulating, 

 its upper face with granulous striae and with several oblique shallow 

 grooves. Pallial line about 7 mm. from ventral margin, well marked, 

 the sinus large and acutely pointed, the space between the pallial 

 Ime and ventral margin radially roughened. Anterior adductor 

 scar deep and with many strongly marked growth lines; posterior 

 scar well marked but not deep, its growth lines hardly visible. 



The type. Cat. No. 347868, U.S.N.M., measures : length, 39 mm. ; 

 lieight, 35 mm. ; diameter, 20 mm. It comes from the Department of 

 Colonia, Uruguay, and was collected and presented by Dr. Florentino 

 Felippone. A specimen in Doctor Felippone's collection, (his No. 

 ]G24) is labelled Rio Urugaiay, Uruguay. It measures: length, 32 

 mm. ; height. 25 mm. ; diameter, 16 mm. 



Two odd valves, Cat. No. 347871, U.S.N.M., from the Uruguay 

 River, Nueva Palmira, Department of Colonia, Uruguay, are more 

 inflated, have a cordate form and have a number of ribs for concen- 

 tric sculpture. More material may show these to belong to a sub- 

 species. 



This is the largest American Corbicula known, the nearest ap- 

 proach to it in size being G. coloniemis Pilsbry, for one specimen of 

 which Pilsbry gives the measurements as : Length, 32^ mm. ; altitude, 

 27i mm. ; diameter, 15* mm. In size and coloring felipponei reminds 

 one of some of the species from the Far East, but of course this species 

 being South American shows a very well-marked sinus near the 

 posterior end of the pallial line. 



CORBICULA (CYANOCYCLAS) FORTIS, new species. 

 Plate 2, figs. 7-9. 



Shell subtriangular. inflated, very thick, especially at the upper 

 portion. Posterior margin long and straight, making a sharp angle 

 with the ventral margin. Anterior margin nearly straight, not quite 

 so long, shortly rounding into the ventral margin, the latter nearly 

 regularly curved. Posterior and anterior ridges both high, the for- 

 mer subangulate, the latter rounded. Posterior area very wide, 

 nearly at right angles to the convexity of the shell. "When the valves 

 are closed their united posterior areas are distinctly wedge-shaped. 

 Beaks high and narrow, well separated. Hinge line greatly arched, 

 especially between the third cardinal tooth and the posterior laterals. 

 Sculpture consisting of numerous fine concentric lines of slightly 

 raised lamellae. Color uniform brownish-olive (Saccardo's olive). 

 Color of interior deep purple, white around the margin. In right 



