PLATE VI. 



Legend. A. Cardinal area. 

 t. Teeth, 

 b'. Sockets, 

 d. Dental lamellae, 

 c. Crura. 



s. Median septum, 

 j. Cardinal process. 



(Figures 1-34, by K. P. Whitfikld.) 



a. 

 a'. 



Pedicle-area. 

 Anterior aiMuctor scars. 

 Posterior adductor scars. 

 Anterior diductoi- scars. 

 Posterior diductor scars. 

 Vascular- markings. 

 Ovarian mai'kings. 



RHIPIDOMELLA, CEhleet. 



Page -208. 



Orthis HYBRiDA, Sowerby. 

 . Figs. 1, 2, 3. Three views of an avei-age individual of the American foi-m referred to this species. 

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



lectly represented, the impression being quadripartite and not flabellate. 

 Fig. 5. The intei'ior of the pedicle-valve; shoysfing the expanded musculai' scars. 

 Niagara group. Lockport, N. Y. 

 For further illusti-ation, see Davidson, Silurian Brachiopoda, plate xxvii, figs. 1-9 ; Hall, Palaeon- 

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

 Hist., pi. xxi, figs. lS-25. 



Okthis Penelope. Hall. 



(See Plate VI a, fig. 10.) 

 Figs. 6, 7, 8. Three views, giving the external characters of a normal mature individual. 

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

 ripartite rathei' than flabellate. 

 Fig. 10. The interior of a small pedicle-valve. 

 Fig. 11. Similar view of an older shell. 



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

 companying senility. 

 Fig. 13. An enlargement of the surface striae ; showing the openings of the oblique tubules upon the stria 

 and the scattered punctae. 



Hamilton group. Western New Ywk. 

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



Orthis Vanuxemi, Hull. 



(See Plate via, 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 Palaeontology 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. Wefteim New York. 

 For further iUusti-ation, see Palaeontology of New York, Volume IV, plate vii, fig. 4. 



SCHIZOPHORIA, King. 



I'age 211. 



Orthis Tioga, Hall. 



Fig. 17. The exterior of a brachial valve. 

 Fig. 18. An intei'nal cast of a pedicle- valve. 



Chemung group. Near Elmlra, N. Y. 

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



