A NEW FEESH- WATER BIVALVE (CORNEOCYCLAS) 

 FROM THE MOUNTAINS OF ECUADOR. 



By Pat L Bartsch, 



Assistant f'itnitnr, IHrision of Mollusk.s. V. H. 'National Museum. 



The species described herewith was collected by Dr. S. Austin 

 Davis, of Gl Biiena Vista avenue, Yonkers, New York, in the valley 

 of the Chanchan River, Ecuador, South America, at an altitude of 

 about 7,000 feet. Of the specific locality Doctor Davis says: 



The Cbaiicban cuts throiigli tlio western Cordillera and empties into the 

 Cliimbo at the base of the western foothills, at a station on the Guayaquil 

 and Quinto Railway called Bucay. The Cbiuibo, after about .55 miles, enters 

 the Gnnyas River a short distance above Guayaquil. The Guayas waters flow 

 to the Pacific Ocean. The tiny stream in which the mollusks were found falls 

 into the Chanchan at about 4,000 feet elevation above the sea (20 miles above 

 Bucay) and takes its rise high up the mountain side, some 3,000 or more feet 

 above tlie entrance to the Chanchan. It is quite a stiff climb to get there from 

 the valley bottom, and in its course there are two or three vertical falls. 



CORNEOCYCLAS DAVISI, new species. 



Shell of medium size, moderately oblique, well inflated, greyish 

 horn-colored with straw-colored ventral margin, having the nepionic 

 portion somewhat constricted off from the post-nepionic part of the 

 shell. Umbones scarcely projecting above the hinge line. Posterior 

 dorsal margin sloping a little more abruptly than the anterior and 

 only about two-thirds as long. Area below the posterior dorsal mar- 

 gin well inflated, that below the anterior dorsal margin somewhat 

 compressed. Posterior border well rounded and evenly curved. An- 

 terior border somewhat produced in the middle and therefore de- 

 cidedly less evenly arched than the posterior. Ventral margin form- 

 ing an even sweeping curve. Entire outer surface marked by deeply 

 incised concentric grooves which are somewhat variable in strength, 

 those on the initial portion of the nepionic shell being finer than 

 those on its margin. The post-nepionic part of the shell is divided 



Proceedings U. S. National Museum, Vol. XXXIII— No. 1 584. 



681 



