NEW URUGUAYAX MOLLUSKS OF THE GENUS COR- 



BICULA. 



By WHiLiAM B. Marshall, 



Assistant Curator, Division of MoUusks. Umied States National iluseiim. 



A large collection of Unigiiayan Corhicula recently received from 

 Dr. Florentino Felippone, of Montevideo, part as a gift to the Ignited 

 States National Museum and part for identification, necessitated a 

 careful study of the South American shells of this genus. At once 

 it became apparent that much of the material received does not fall 

 into any of the known species and in order properly to classify them, 

 it became necessary to describe the eight new species herein named. 

 A specimen and an odd valve from Mr. S. Olea, of Montevideo, have 

 lain in the collection unidentified for about 18 years An odd valve 

 of the same kind just received from Doctor Felippone further con- 

 firms the belief that these shells belong to a new species which is 

 herein described under the name oleana. The preeminent Corhicula 

 of the Uruguayan and southern Brazilian region is limosa ISIaton, the 

 first species described. It seems to be the most abundant CorhicuUi 

 in the region, but there may be several species or subspecies included 

 under this name. Surely the shells placed here exhibit a wide range 

 of variation in form, size, and color. Some of the southern Brazilian 

 forms are long, but little resembling the typical triangular forms. 

 Abundant material and a study of the distribution in the various 

 river systems is needed to clarify this species. 



The narrow radiating lines of color (usually reddish or chestnut) 

 so often seen in some of the species deserve some notice. In speci- 

 mens of the same species they may or may not be present. They 

 seem to be in the periostracum but in fact they are in the calcareous 

 portion of the shell and are seen through the periostracum. The 

 collection of the National Museum contains a number of specimens 

 in which part of the periostracum has been rubbed away and in 

 which the color rays are very prominent on the calcareous part thus 

 exposed to view. No color rays are to be seen in the periostracum 



No. 2552.— Proceedings U. S. National Museum. Vol. 66, Art. 15. 



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