b PEOCEEDINGS OF THE NATIONAL MUSEUM vol. 72 



CORBICULA (CYANOCYCLAS) IHERINGI, new species 



Plate 1, figs. 11, 12 



Like C . coloniensis in color and to a great extent in form, but the 

 posterior ridge not so marked, the posterior area less wedge shaped, 

 the cardinal teeth relatively smaller and the lateral teeth relatively 

 longer and thinner. 



The type (Cat. No. 171423, U.S.N.M.) consists of a single valve. 

 It measures: Length, 22 mm.; height, 18.5 mm.; diameter (if both 

 valves were present) would be 12 mm. It comes from S. Leopols, Rio 

 Grande, do Sul, Brail, and was presented by Dr. H. von Ihering. 



This may prove to be a subspecies of C. coloniensis^ its variation 

 from type due to a distant habitat. 



CORBICULA (CYANOCYCLAS) PLATENSIS, new species 



Plate 1, figs. 7, 8 



Shell subequitrangular, thick, inflated, obliquely truncate pos- 

 teriorly extended and sharply rounded anteriorly, dorsal line much 

 arched, ventral margin evenly rounded, curving regularly into the 

 anterior margin and angularly into the posterior margin. Both the 

 anterior and posterior aspects wedge shaped, wide, and rounding into 

 the convexity of the shell. Beaks high, located at the middle of the 

 dorsal line, pointing forward. Posterior ridge high but rounded, 

 the descent to the posterior margin rapid. Anterior ridge gradually 

 rounded. Posterior end of shell slightly nasute. Beaks eroded, 

 white at the tips and then deep purple. General color dark chestnut 

 on a clothlike periostracum, the dorsal area slightly lighter. Several 

 scarcely visible dark radiating lines. Interior mostly purplish, the 

 cardinal teeth white, the lateral teeth and an area at the front and 

 one at the rear delicate pink. Concavity pale purple, area between 

 ventral border and pallial line deep rich purple rayed with white; 

 a wide purple ray marking the posterior angle. In the right valve 

 the anterior cardinal tooth is thin, platelike and very oblique; the 

 middle tooth is thick and deeply bifid ; the posterior tooth moderately 

 thick, indistinctly bifid and oblique. In the left valve the anterior 

 tooth is thicker than in the right valve, the middle tooth thick and 

 slightly bifid, the posterior tooth thin. In right valve there are two 

 anterior and two posterior lateral teeth, the inner ones crenulated. 

 The left valve with one anterior and one posterior lateral tooth, the 

 former the smaller, the latter very high, and both of them very 

 sharply crenulated. Adductor scars not very prominent, sinus well 

 marked, deep, and sharply pointed. 



The type (Cat. No. 365393, U.S.N.M.) measures: Length, 26.5 

 mm. ; height, 23.5 mm. ; diameter, 17.5 mm. It comes from the Bay 



