I'LATK Vis— Continued. 



HETERORTIilS, nom. nov. 



Page '202. 



Oiri'His Clytie, Hall. 



Fig'. 20. A view of the bi-achial valve of the type-siiecimen ; showing the area and foramen of the pedicle- 

 valve. 



Fig:. 21. The interior of a pedicle-valve ; showing- the elongate scars of the cardinal muscles and the small 

 adductor impi-essions. 



Fig. 22. The inteiior of the brachial valve. The cai-iliiial i^rocess is simple, but very high, and the crural 

 plates are much elevated, terminating abi-iiptly. Muscular area small and oVjscui-ely quadri- 

 partite. 



Fig. 23. The articular area of the same valve ; showing the divisions of the inu.scular area. X 2. 

 Fig. 24. The surface ornamentation, consisting of a fasciculate grouping of the railiating sti-ise, ci'Ossed by 

 minute concentric lines. X 4. 



Trenton horizon. Npmt Fraiihf()rt, Ky. 



DALMANELLA., nom. nov. 



Page 205. 



Orthis Evadne. Billings. 



Fig. 2.5. A view of the brachial valve of the type-specimen ; showing area and foramen of opposite valve. 

 Fig. 26. The opposite side of the.same specimen. 



" Point Levis ; in the wppei- part of Limestone No. 2, Quebec gronp." 



Okthi.s testudinaria, Dalnian. 



Figs. 27, 28, 29. Three views of a small form which may prove to be a permanent variety of the species. 

 Fig. 30. The interior of the pedicle-valve of the same form. 

 Fig. 31. The interior of the brachial valve. X 2. 



Trenton horizon. Mineral Point, Wisf07isin. 

 Fig. 32. The exterior of the pedicle-valve of a noi-mal individual. 

 Fig. 33. The exterio)- of the brachial valve of a somewhat larger specimen. 

 Fig. 34. A profile of the same. 



Fig. 35. The inteiioi' of a pedicle-valve ; showing the character of the muscular area. 

 Fig. 36. The interior of a brachial valve, i-etaining the articulating apophyses and the subdi\dsion of the 



musculai' area. 

 Fig. 37. The central cardinal portion of a similar valve, enlarged to show with gi-eater distinctness the 

 structui-e of the articulating aparatus. 



Hudson River group. Cincinnati, Ohio. 

 Fig. 38. The interior of a large pedicle-valve. 



Tj'enton limestone. Middleville, iV. Y. 

 Pig. 39. The interior of a brachial valve. X 2. 



Trenton limestone. Lowville, N. Y. 



