PLATE VI— Continaed. 



RIIIPIDOMELLA, CEhlert. 



rage -208. 



Orthis Owkni. sp. IIOV. 



(See Supjilemeiil for liesrriptiouj 

 Fig. 19. The exterior of a brachial valve. 

 Figs. 20, 21. Interioi-s of pedicle and l)rachial valves, respectively. 



" Knobstone group" of Owen, — age of the Waverly. Butfon-^iumld Knobs, Kentucky. 



8CHIZ0PH0RIA, Kisa. 



Page 211. 



Ortuis cari.vata, H:ill. 



Fig. 22. An internal cast of a pedicle-valve ; showing the character of the muscular ai-ea, at the anterior 

 margin of which are seen traces of the vascular sinuses. 

 Chemung gi'oup. JVear Painted Post, N. T. 

 For further illustration, see Palaeontology of New York, Volume IV, ]>Iate viii, figs. 30-32. 



Orthis 8wallovi. [l:ill. 



Figs. 23, 24. The exterior and interior of the jiedicle- valve. 



Burlington limestone. Burlington, Iowa. 



Orthis Tulliensis, Hall. 



Figs. 25, 26, 27. Three views of a normal iiidividnal ; showing the great convexity of the bratthial valve 



and the shallow pedicle-valve. 

 Fig. 28. An internal cast of the brachial valve; showing the (juadrtiple niustnilar impression and the prin- 

 cipal vascular trunks. At y is the tilling of the rostral cavity of the opjiosite valve. 

 Fig. 29. An internal cast of the pedicle-valve. 



Tully limestone. Keuka Lake, N. Y. 

 For further illustration, see PalsEontolog}' of New York, Volume IV, plate vii, fig. 5. 



Orthis propinqua, Hall. 



Fig. 30. An internal csist of the brachial valve. The subdivision and the coui-se of the vascular sinuses 

 ai-e very sharply retained. 



Corniferous limestone. Avmi, N. Y. 

 For further illustration, see Palaeontology of New York, Volume IV, plate v, fig. 3. 



Orthis impressa, Hall. 



(See Plate VI a, figs. 26, 27.) 

 Fig. 31 . An internal cast of the pedicle-valve ; showing the subdi\-isions of the muscular area, and the un- 

 usual arrangement of the vascular sinuses. 

 Chemung group. 

 For further illustration of this species, see Paleontology of N.Y., Volume IV, pi. viii, figs. 11-19. 



OKTHOSTROPHIA, Hall. 



Page 199. 



Oktiiis strophomenoides. Hall. 



(Ser Plate Va, tigs. 24-27.) 

 Fig. 32. The exterior of an imperfect lirachial valve. 

 Fig. 33. An internal ca.st of the pedicle-valve ; showing the vei-y small muscular area, the ovarian mai-k- 



ings in the umbo-lateral regions, and the vascular sinuses over the pallial ivgion. 

 Fig. 34. An internal cast of the brachial valve, retaining the inipre.'^ion of the simple cardinal process, and 

 showing the four sharply defined adductor scai-s, the ovarian markings and the ramified vascu- 

 lar sinuses. 



Lower Helderberg group. Near Clarksville, iV. Y. 



