BRACHIOPODA. 175 



cular attachments. Crescent distinct, terminal scars very prominent. 

 Brachial valve with the umbonal region nnich thickened ; the platform 

 sharply V-*^li'ip6tl> its anterior wall beini;' considerably excavated to Ibrm 

 imperfect vanlts ; the wliole elevation is situated somewhat further forward 

 than the opposite valve. A faint longitudinal septum extends a short dis- 

 tance forward from the apex of the platform. Crown of the crescent faint; 

 terminal scars as in the pedicle-valve. 



From tlie magnesian limestone of the Niagara .group, near Cedarburgh, Wis- 

 consin, in association with Diiiobolus Conradi, Monomer ella prisca and M. Greenii. 



MONOMERELLA OrTONI, sp. HOV. 

 I'LATE IV c, FIGS, li, 15. 



Pedicle-valve large, with a high cardinal area, which is gently incurved longi- 

 tudinally and crossed by lamellose growth-lines, upon which the evidences 

 of the deltidial ridges are extremely faint or altogether wanting. Umbonal 

 cavities conspicuous, but much shorter than is usual in M. prisca. Cardinal 

 slope large, triangular and divided by an axial furrow. Cardinal buttress 

 broad at the base but not especially prominent. Platform apparent only at 

 its anterior edge where it has a broad anterior slope. Crescent well defined 

 beneath the hinge-line ; terminal scars very prominent ; central, lateral and 

 anterior impressions discernible on the platform. Pallial sinuses very strong, 

 the outer ramifications from which are distinctly seen. 

 Brachial valve unknown. 



From the Niagara dolomitic limestone, at tlu; Rising Sun quarries, Wood 

 count)/, Ohio. 



MoNOMERELLA EgANI, sp. IIOV. 

 I'LATE IV c, FIG, 16 



Brachial valve with an unusually high cardinal area, indicating a quite ele- 

 vated beak. This area is strongly striated transverseh', and bears two faint 

 longitudinal depressions corresponding in position to the deltidial ridges of 

 the pedicle-valve. It is continued laterally nearly to the middle of the 

 margins. Crescent very narrow over the crown, lying close upon the car- 

 dinal line ; at its turn forward it is developed into a deep, narrow, elongate 



