BRACHIOPODA. 369 



which very gradually increase by implantation and become more numerous 

 anteriorly. These plications are of slightly unequal size, which appears to be 

 due to variation in the rate of their multiplication. In the umbonal regions 

 the plications are obsolete. 



Niagara dolomites. Near Milwaukee, Wisconsin. 



CONCHIDIUM CRABSIPLICA, sp. nOV. 

 PLATE LXVI. FIGS. 24, 2S. 



Shell elongate, subelliptical in outline. Valves subequally convex, depressed 

 above ; cardinal slopes broad and abrupt on both. Umbo of the pedicle-valve 

 erect, not prominent ; surface slightly elevated medially. Umbo of brachial 

 valve depressed, apex concealed ; median region depressed anteriorly ; surface 

 of both valves bearing broad rounded plications, separated by deep grooves. 

 Of these plications there are from eight to ten on each valve over the pallial 

 region ; by dichotomizing these become more numerous anteriorly. 



Niagara group. Near Louisville, Kentucky. 



CoNCHiDiUM Geokgi.®, sp. nov. 



PLATE LXVr, FIGS. 18, 19. 



Pedicle-valve unknown ; brachial valve trilobed by the development of a 

 strong median fold which extends from apex to margin, and is sharply delim- 

 ited by abrupt lateral slopes. The sides of the valve are convex, rather narrow, 

 and slope abruptly to the lateral margins. Umbo full and incurved. Surface 

 covered with numerous duplicating plications, of which from fifteen to twenty 

 may be counted on each side at the margins, and twelve to fourteen in the 

 fold. 



Clinton group. Trenton, Georgia. 



Capellinia mira, sp. nov. 



PLATE T-XX, FIGS. 6-14. 

 (See pages 248, 249.) 



