I'LATE V A— Continued. 



Oktxiis roucATA, McCoy. 



Figs. ^0, 21. Brachial and i^rofile views of an avej'age example ; showing the rotundity of the brachial valve 

 and the resupination of the opposite Ijeak. 



Middle Silurian. Junction Cliff, Anticosti. 

 Foi' further illustration, see Davidson, Silurian Brachiopoda, plate xxxii, figs. 12-20. 



ORTHOSTEOPHIA, Hall. 



Page 199. 



OiiTiiis Halli. Siiffoi-d (?^0. slrojjhomenoides, Hall). 



Fig. 22. A view of the pedicle-valve. 



Fig. 23. A cardinal view of the conjoined valves of the same sjiecimen. 

 Lower Helderberg group. Pm-ry county, Tennessee. 



Orthis strophomenoides, Hull. 



See Plate VI, figs. 32-34. 

 Fig. 24. The exterior of a brachial valve. 

 Fig. 2.^. A cardinal view of the same specimen ; showing gi-eater convexity than the preceeding species. 



(The relative position of the valves as represented in the figures 23 and 25 is revei'sed.) 

 Fig. 26. The inteiior of a bi'achial valve ; showing the character of the cardinal pi'ocess, musculai- area, 



ovarian and vascular mai-kings. 

 Fig. 27. The interior of the opposite valve. The muscular area is gi'eatly thickened and is divisible into 

 the adductor and diductoi- elements; the vascular sinuses are also very distinct. 

 Lower Helderbei'g gi'oup Near C'larJtsville, N. Y. 

 For fai'ther illusti'ation, see Pal;EontolOgy of New York, Volume III, plate xxiii, fig. 7. 



PLiESIOMYS, NOM. NOV. 



P.-ige 19C. 



Orthis deflecta, Coiivud. 



Figs. 28, 29. The exterior of the brachial and pedicle-valves. 



Fig. 30. A cardinal view of the same sjiecimen ; showing the elevation of the area, the convex deltidium, 

 and the convexity of the brachial valve. 



Trenton hoi'izon. Dixon, Illinuis. 

 For further illustration, see PalEeontology of New York, Volume I, plate xxxiB, fig. 5. 



Orthis loricula, sp. uov. 



Fig. 31. The cardinal area of the pedicle-valve ; showing the deltidium. 



Fig. 32. The exterior of the pedicle-valve. 



Fig. 33. The interior of the brachial valve. The delthyrium is filled by a callosity which also supports 



the crural jilates and the linear cai'dinal pi'ocess ; the deltidium is also present in an incipient 



condition. 

 Fig. 34. The intei-ior of the pedicle-valve ; showing the character of the muscidar area, ovarian markings, 



etc. 



Galena limestone. Fountain, Minnesota. 



Orthis Holstoni, Safford. 



Fig. 35. Pi'ofile of the type specimen. 



Fig. 36. Cardinal view of the same ; showing the wide delthyrium and elevated area of the pedicle-valve. 



Fig. 37. A view of the brachial valve of the same specimen. . 



Trenton horizon. Near Knoxville, Tennesee. 



Orthis Saffordi, sp. uov. 



Figs. 38, 39, 40. Thi'ee views of the exterior of a specimen ; showing its general form and the character of 

 its surface markings. 



Trenton horizon. Near Knoxville, Tennessee. 



