PluATE IV B— Continaed. 



Okbicii-oidea Randai.tj, Hall. 



Fi{r. IS. The exterior of a peiliole-vahe ; showing-, from compression, the jipical nui-scular riiig-e, the 

 railiating' pallial siniise.-i and the internal track of the peiiiele-furrow extending- toward the 

 inarg^jn and inteirupting- the concentric g-rowth-lines. The overlappin;^ niai-g-inal portion of the 

 opposite valve is .seen about the po.sterior arc of the circumference.. Natural size. 

 Hamilton grou]). Kear ffrholiarh, JV. Y. 



Obiculoidea PULCHRA, .sp. IIOV. 



Fig-. V.K The exterior of a |)edicle-valve. X 1.5. 

 Cuyahoga shale. Berea, Ohio. 



Qrbiculoiuea Manhattanensis, Meek mid Haytleii. 



Fig. 20. The interior of a pedicle-valve : showing the character of the pedicle-area, the radiating vascular 

 lines, and whei-e the shell is bioken on the anteiior portion, the character of the external 

 ornamentation and the unu.sual thii-kncss of the valve. 

 Coal Measures. Riley county, Kansax. 



(EHLERTELLA, s.-gen. nov. 



Page 120. 



GDhlektella pleurites. Meek. 



Fig. 21. The intei-ior of a pedide-valvo ; showing the elevated pedicle-ridge and the open, marginal fora- 

 men. Natui'al size. 

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



Figs. 28, 24. Biachial valves, tlifjering slightly in outline, and showing the posterior position of the apex. 

 Waverly group. Newark, Ohio. 



LlXDSTKfEMELLA, s.-gen. nov. 



Page 120. 



Lindstru;mella aspidium, .sp. iiov. 



Fig. 2,5. A brachial valve, from which the shell is largely exfoli.ated, but retaining sufficient to show the dis- 

 tinct, elevated, concentric ri<lges characterizing the external surface. The great lateral ridges 

 and the fainter median septum are rejiresented by fui-rows. At the posterior exti'emities of the 

 formei- are seen two small subcircular muscular impressions, while the scars of the anterior 

 adductors are strongly developed. Natural size. 



Fig. 2t>. The counterpart of the same ; drawn from a gutta-percha impiession, showing all the internal 

 characters in theii- n.atuial relief. 



Hamilton group. Nfar Hamilton, N. Y. 

 Fig, 27. A natural ca.-it of the extei-ior of a lai-ge 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 pedicle-area. The pedicle-passage ditl'ers from that in the normal mature 

 Oi!Blcri,oiDEA, in not being closed, though its margins appear to be in contac;t. The charactei-s 

 of this area as repiesented in the diawitig, have been slightly restored from other specimens. 

 Hamilton group. JVrar Leonardsville, N. Y. 

 Fig. 28. A small pedicle-valve, with the charactei-istic ornamentation and strongly developed foraminal 

 groove. 



Hamilton group. Near Darien, N. Y. 



KCJ^MERELLA, s.-gen, nov. 



Page 1-20. 



Rcemerella ghandis, Vaiuixeni. 



Fig. 2!l. The exterior of a brachial valve. 



Hamilton limo.stone. Falls of the Ohio. 

 Fig 30. The interioi-of a pedicli'-valve fi-om which the shell has been parti.dly exfoli.ated, exposing the 

 matrix and the cast of the external peilicle-gi-oove. 



Fig. 31. Th(> counterpart of the same specimen, from a gutta-percha cast; showing all the e.ssential ex- 

 ternal characters. The extreme depression of the anterior portion of the valve and the cor- 

 respondingly great elevation of the pedicle-area are features subject to some slight variation 

 within the limits of the species. 



Hamilton grouj). CazeTiovia, N. Y. 



