PLATE IV E— Continued. 



OKBicui-otnEA Raxdalu, Hall. 



Fiir. IS. The I'xterioi- of a pecUcle-valve ; showing-, from compression, the apical muscular ridge, the 

 i-ailiating- pallial sinuses ami the internal track of the pedicle-furrow extending- toward the 

 margin and interrupting the concentric gi-owth-lines. The ovei-lap]iing marginal portion of the 

 opposite valve is seen about the postei-ior arc of the circumference. Natui-al size. 

 Hamilton groaj). Kear ffcltn/idrii, W. Y. 



Obiculoidea pulohra, .sp. nov. 



Fig. 19. The e.xterior of a ])edicle-valve. X 1-5. 

 Cuyahoga shale. Bet-ea, Ohio. 



Orhiculoidea AIanhattanknsls, Meek uiid Hay den. 



Fig. 20. The interior of a pedicle-valve ; showing the character of the pedicle-area, the i-adiating vascular- 

 lines, and where the shell is broken on the anterior portion, the character of the external 

 ornamentation and the unusual thickne.ss of the valve. 

 Coal Measiu-es. Riley county, Kansas. 



(EHLERTELI.A, s.-gen. nov. 



Page 120. 



G^hlertella pleurites. Meek. 



Fig. 21. The interior of a pedicle- valve ; showing the elevated jiedicle-ridge and the open, marginal fora- 

 men. Natural size. 

 Fig. 22. ProKle of the same, giving the internal elevation of the pedicle-area. 



Figs. 2iJ, 24. Brachial valves, differing slightly in outline, and .showing the po.sterior position of the apex. 

 Waverly group. Newark, Ohio. 



LlNDSTRa:MELI,A, s.-oen. nov. 



Page 1-20. 



Lind8tru-:mella aspidium, sp. nov. 



Fig. 25. Abt-a(-hial valve, from which the shell is largely exfoliated, but retaining sufficient to show the dis- 

 tinct, elevated, concentric ridges characterizing the exteriuil surface. The great lateral ridges 

 and the fainter median septum are i-eju-esented by furrows. At the posterior extremities of the 

 former are seen two small subcircular muscular impie.ssions, while the scai-s of the anterior 

 adductors are strongly developed. Natui-al size. 



Fig. 26. The counteri)art of the same ; drawn froni a gutta-percha imju-essiou, showing all the internal 

 characters in theii- natural relief. 



Hamilton group. Ni-ar HiviaiUon, N. Y. 



Fig, 27. A natui-al cast of the exterior of a large pedicle-valve believed to belong to this species; showing 

 the character of the surface ornamentation, and the peculiar undulation of the concentric ridges 

 on approaching the peilicle-area. The ijedicle-pa-ssage ditt'ers IVom that in the normal mature 

 Okbicvloidka, in not lieing closed, though its margins ajipear to be in contact. The characters 

 of this area as represented in the drawing, hiive been slightly restored from other specimens. 

 Hamilton group. Nfctr Lennardsville, N. Y. 



Fig. 28. A small pedicle-valve, with the charactei-istic ornamentation ami sti-ongly developed foraniinal 

 groove. 



Hamilton grouji. Near Darien, N. Y. 



RCEMERELLA, s.-gen. nov. 



Page VH). 



RfEMERELLA GRANDis, Vanii.xeni. 



Fig. 2'.l. The exterior of a brachitil valve. 



Hamilton limestone. Falls of the Ohio. 

 Fig :i(i. The interior of a pedicle-valve from which the shell has been partially exfoliate<l, exposing the 



matrix and the cast of the external pedicle-groove. 

 Fig. :!l. The counterpart of the same specimen, from a gutta-percha cast; showing all the essential ex- 

 tei-rial i-liaractei-s. The extreme depression of the antei-ior poi-tion of the valve and the cor- 

 resi)on<lingly great elevation of the pedicle-area are features subject to some slight variation 

 within tiie limits of the species. 



Hamilton grou)). C'azenovia, N. Y. 



