PLATE LXVI. 



(Figures 1-5, U, 13, 11, 1(M!(, -i^-'i"! hy K. K.mmiins ; i;, s, 10 liy It. I'. Willi rii;i,i) ; 7, li liy F. S. Swinton ; li, M-ii 



h\ u. |{. Simpson.) 



Genus CONCIIIDIUM. \assL 



I'age -IM. 

 CONOHIDIUM UNGUIFORMIS, Ullicll. 



Figs. 1-3. Dor.>siil, cardinal anil ventral view.s of the original specimen ; .sliiiwiiiy the form of the siiell, the 

 character of itt< [plication, it."* concentric varices ami tine f;rowth-line.«. The ilra\vin(,'S are 

 slightly restored in the iinibonal region of the pedicle-valve. 



Kig. 4. A lateral view of the .same s])e(;imen, in which the median .septum and siiomlyliom of the pedicle- 

 valve are exposed. 



Niagara group. Near LuuisvUlc, Ketituckii. 



CoNCHiDiUM, .sp. indi'f. 



Fig. 5. An internal cast of a small pedicle-valve, with a coarsely plicated siirfa<;e ; showing the apical 

 portion of tlie (illing of the spondylium and a somewhat distorted median septum. 

 Niagara dolomites. Near Milwaukee, WiscoJi.thi. 



CONCHtDIUM EXPONENS, !i\). IIOV. 



Figs. 0-9. Inteiiors of pedicle (tigs, 6, 7) and brachial (tigs. 8, 9) valves of a strongly costate shell ; sho\ving 

 the structure of the interioi'. 



Niagara group (Halysites Ijed). Louixrille, Kentucky. 



CONCIHUIUM MULTICOSTATUM, Hull. 

 See Plate 64. 

 Fig. 10. A profile of the onginal specimen, an internal cast. 



Niagara ilolomites. Wauvaiitotta, fViftcoiiJiiii. 



CONCHIlJll.M lilLOCULARK. LillJie. 



Fig. 11. Dorsal view of an average example ; showing the form of the shell, character of the surface, and 



retaining a portion of the deltidium. 

 Fig. 12. A profile of the same specimen ; showing the long, coiii'ave and smooth cardinal slopes. 

 Fig. 18. A natural longitudinal section of conjoiiHMl \al\'es; showing the relation of the spondylium and 



septal ]ilates. 

 Fig. 14. Ventral view of the same individual ; showing the length of the meili.nn septum. 

 Upper Silurian limestone. Inland of Gntland. 



CONCHIUIUM DECUSSATUM, WilitcilVOS. 

 See Plate 65, figs. 1. 2. 

 Fig 15. Dorsal view of a small example ; sho^ving the foi'm and exterior chai-actei-s of the species. 

 Niagara dolomites. Rapicls of the i?askatcheioan liUvr, British America. 



CONCHIDIUM COLLETTI, j\IilU'|-. 



Figs 16, 17. Ventral and proHle views of a pedicle-valve ; showing the line pliiation. freiiuent imiiricating 

 growth-varices, and the expanded anterior margin. 

 Niagara limestone. Indiana. 



CONCHIDIUM GeORGI/E, .sp. IIOV. 



Figs. IS, 19. Dorsal and cardinal views of the brachial valve ; showing the conspicuous median fohl and 

 the plication of the siu'face. 



Clinton group. Trentim, Georgia. 



