Feb., 1846.] 23 



Monotis Poulsoni. Plate 1, fig. 32. Suborbicular, ventricose, not oblique, 

 ribs about 44 in number, obtusely rounded, interstices nearly flat, about as 

 wide as the ribs, with minute transverse wrinkles ; umbo broad and the 

 summit prominent; anterior and posterior margins rounded. 



Locality. Jersey shore, Lycoming county, Pennsylvania. (Devonian 



shale.) 



This beautiful species occurs in a dark shale of the same geological age 

 and appearance as the shale of the Chemung Narrows in New York, which 

 i3 a part of the Devonian System. 



It is dedicated to my friend Charles A. Poulson, Esq , to whose splendid 

 collection it belongs. 



M. elevata. Plate 1, fig. 31. Obliquely oval, somewhat ventricose, ribs 

 about 42 in number, prominent, acutely rounded, interstices very narrow, 

 except towards the anterior hinge margin, where the ribs are larger ; an- 

 terior and posterior margins nearly straight ; anterior side very short. 



Locality. Occurs with the preceding species in the same rock. 



Cabinet of Mr. Poulson. 



SILURIAN SPECIES. 



AVICULA. 



Avicula ferruginea. Plate 1, fig. 28. Subrhomboidal ; left valve pro- 

 foundly ventricose ; anterior side profoundly contracted ; umbo very promi- 

 nent ; extremity of anterior wing angulated ; the margin beneath slightly 

 emarginate ; margin of posterior wing straight and direct. 



Locality. Jersey shore, Lycoming county, Pennsylvania. 



Cabinet of Mr. Poulson. 



This speeies abounds in the Fossiliferous iron ore of the Middle Silurian 

 series. 



CARBONIFEROUS SPECIES. 

 Strophomena. 

 Strophomena nassula. Hinge area wide ; valve3 with approximate acute 

 radiatiDg strise, and finer concentric lines ; one valve flat, with three or four 

 large concentric undulations. 



Locality. Jersey shore, Lycoming county, Pennsylvania. Mr. Poulson. 



RECENT SHELLS. 

 Cyrena. 

 Cyrena Floridana. Plate 1, fig. 1. Triangular, subequilateral, ventricose : 

 summits prominent, concentrically striated ; posterior side with an obtust 

 fold near the margin ; color whitish, varied with violaceous, both externally 

 and internally. 

 Locality. Tampa Bay, Florida. 



