PLATE VI—Continued. 
RHIPIDOMELLA, GEhlert. 
Page 208. 
Orthis Oweni. sp. nov. 
(See Supplement for description.) 
Fig. 19. The exterior of a brachial valve. 
Figs. 20, 21. Interiors of pedicle and brachial valves, respectively. 
“ Knobstone group” of Owen, = age of the Waverly. Button-mould Knobs, Kentucky. 
SCHIZOPHORIA, King. 
Page .211. 
Orthis carinata, Hull. 
Fig. 22. An internal cast of a pedicle-valve ; showing the character of the muscular area, at the anterior 
margin of which are seen traces of the vascular sinuses. 
Chemung group. Near Painted Post, N. Y. 
^ For further illustration, see Palaeontology of New York, Volume IV, plate viii, figs. 30-32. 
Orthis Swallovi, Hull. 
Figs. 23, 24. The exterior and interior of the pedicle-valve. 
Burlington limestone. Burlington, Iowa. 
Orthis Tulliensis, Hall. 
Figs. 25, 26, 27. Three views of a normal individual; showing the great convexity of the brachial valve 
and the shallow pedicle-valve. 
Fig. 28. An internal cast of the brachial valve; showing the quadruple muscular impression and the prin¬ 
cipal vascular trunks. At y is the filling of the rostral cavity of the opposite valve. 
Fig. 29. An internal cast of the pedicle-valve. 
Tully limestone. Keuka Lake, N. Y. 
For further illustration, see Palaeontology of New York, Volume IV, plate vii, fig. 5. 
Orthis propinqua, Hull. 
Fig. 30. An internal cast of the brachial valve. The subdivision and the course of the vascular sinuses 
are very sharply retained. 
Corniferous limestone. Avon, 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 subdivisions of the muscular area, and the un¬ 
usual arrangement of the vascular sinuses. 
Chemung group. 
For further illustration of this species, see Palaeontology of N.Y., Volume IV, pi. viii, figs. 11-19. 
ORTHOSTROPHIA, Hall. 
Page 199. 
Orthis strophomenoides, Hull. 
(Sefe Plate Va, figs. 24-27.) 
Fig. 32. The exterior of an imperfect brachial valve. 
Fig. 33. An internal cast of the pedicle-valve ; showing the very'small muscular area, the .ovarian mark¬ 
ings in the umbo-lateral regions, and the vascular sinuses over the pallial region. 
Fig. 34. An internal cast of the brachial valve, retaining the impression of the simple cardinal process, and 
showing the four sharply defined adductor scars, the ovarian markings and the ramified vascu¬ 
lar sinuses. 
Lower Helderberg group. Near Clarksville, N. Y. 
