PLATE VI. 



(Figul■e^ 1-W, l>y H. 1'. Wm iKiEi.iJ.i 



Legend. A. Cardinal area. 

 t. Teeth, 

 b'. Sockets, 

 d. Dental lamellffi. 

 c. Crura. 



s. Median septum. 

 j. Cardinal process. 



p. Pedicle-area. 



a. Anterior adiluctor scars, 

 a'. Posterior adductor scars. 



!•. Antei'ior diductor scars, 

 r'. Posterior didnc'tor scars. 



V. Vasculai- markings. 



o. Ovarian markings. 



Figs. 

 Fig. 



Fig. 

 Fig. 

 Fig. 



RHIPIDOMELLA, CEhlert. 



I'.ifre 208. 



OuTHis HYBRiDA, Sowerby. 

 Figs. 1, 2, 3. Three views of an average individual of the American form referred to this species. 

 Fig. 4. The interior of the brachial valve. The character of the diductor muscular scai-s is here incor- 

 rectly repre.sented, the impression being quadripartite and not tlaliellate. 

 Fig. 5. The interior of the pedicle-valve; showing the expanded muscular scars. 

 Niagara group. Lockport, N. Y. 

 For further illustration, see Davidson, Silurian Bi'achiopoda, plate xxvii, figs. 1-9 ; Hall, Palseon- 

 tology of New York, Volume II, plate lii, tig. 3 ; Twenty-eighth Rept. N. Y. State Mus. Nat. 

 Hist., pi. xxi, tigs. 18-25. 



Okthis Penelope. H;ill. 



(See Plate VI a, fig. 10.) 

 6, 7, 8. Three views, giving the external characters of a normal mature in<lividual. 

 9. The interior of a brachial valve ; showing the articulating apparatus. The muscular area is quad- 

 ripartite rather than tlabellate. 



10. The interior of a small pedicle-valve. 



11. Similar view of an older shell. 



12. The interior of a pedicle-valve, which shows the thickening about the muscular impressions, ac- 

 companying senility. 



Fig. 13. An enlargement of the surlace striie ; showing the openings of the oblique tubules upon the stria; 

 and the scattered punctis. 



Hamilton gi-oup. Western, New Ym-Jc. 

 For further illustration, see Palaeontology of New York. Volume IV, plate vi, fig. 2. 



Orthis Vanuxemi, Htill. 



(See Plate VI A, figs. 7, 8.) 

 Fig. 14. An enlargement of the surface striae. 



Fig. 15. An internal cast of the pedicle-valve ; showing the pedicle-scar and othei- muscular impressions. 

 Hamilton group. Cumberland, Maryland. 

 For further illustration, see Palseontology of New York, Volume IV, plate vi, fig. 3. 



Orthis Leucosia, Hall. 



(See Plate VIA, fig. 9.) 

 Fig. 16. The interior of the pedicle-valve. 



Hamilton group. Western New York. 

 For further illustration, see Palaeontology of New York, Volume IV, pljite vii, fig. 4. 



SCHIZOPHORIA, King. 



Page 211. 



Orthis Tioga, Hall. 



Fig. 17. The exterior of a brachial valve. 

 Fig. 18. An internal cast of a pedicle-valve. 



Chemung group. Near Elmira, N. Y. 

 For further illustration, see Palaeontology of New York, Volume IV, plate viii, figs. 20-29. 



