30 PROCEEDINGS OF THE ACADEMY OF 



anterior to the beak, and two or three very small direct teeth 



under the beak. 



T. longula (Young), Conrad, PI. I., fig. 13. 



Rhomboidal, compressed, alated, anterior margin obliquely 

 rounded; umbo slightly convex, plicated, the plicfe similar to the 

 preceding, but the zigzag transverse ones wanting. 



There are only fragments of this shell before me, and there- 

 fore the outline must necessarily be conjectural. 



OSTOMYA, Conrad. 



Thin, concentrically plicated ; hinge with a spoon-shaped ob- 

 lique fosset in the left valve, and a small tooth near the apex ; 

 right valve cartilage fosset very oblique, almost parallel with the 

 hinge line. 



0. papyria, Conrad, PI. I., fig. 6. 



Subovate, inequilateral, compressed, very thin, concentrically 

 plicated, slightly sinuous anteriorly; ventral margin slightly 

 emarginate anteriorly ; umbonal slope undefined ; posterior end 

 subangular. 



A very rare shell, of the family Anatinidae. The fosset is very 

 large in proportion to the size of the shell. This form of hinge 

 would indicate a genus living in water more or less brackish. In 

 one specimen the apicial tooth is tuberculiform, in the others acute 

 with a slight channel anterior to it. 



o 



NUCULANA ? Link. 



Plate I., fig. 2, represents the outline of a single specimen of a 

 shell having the form and somewhat similar hinge of Nuculana. 



PLANORBIS, Guettard. 

 P. Febasana, Conrad. 



Discoid, depressed ; volutions 3, convex, channelled along the 

 suture, glos.sy ; base concave, volutions rounded, separated by a 

 deep channel ; aperture round. 



Four or five specimens of this very small species were found in 

 a quantity of small shells and fragments of shells. They ai-e as 

 fresh-looking as living species. If some of these Pebas fossils 

 were gathered, washed out of the clay on the shore of the Amazon, 

 the collection might include recent species of the vicinity. 



