PLATE Va. 



(Figures 2, i, 16-31, 24-tO by E. EJOtONS ; 1, 3,5-14 by E. P. Whitfield; 15 by F. B. Meek; ii by I'Hiui' AsT ; 



23 by J. C. McCONNELL. ) 



Legend. A- Deltidium. a'. Posterior adductor impressions, 



j. Cardinal p]-ocess. i-. Diductor muscular impi'essions. 



fp. Crural plate. p. Pedicle-muscular impression, 



t. Teeth. o. Ovarian impi'essinns. 



b. Sockets. v. Vascular mai'king's. 



a. Antei-ior adductoi' impressions. 



HEBERTELLA, nom. nov. 



Page 193. 



Oethis sinuata, Hall. 



Fig. 1. The interior of a pedicle-valve; giving the character of the muscular area, ovarian and vasculai' 



markings. 

 Fig. 2. An enlargement of the muscular area of the pedicle-valve ; showing the large diductor (»•), lineal 



central adductor (a) and the pedicle-scar (p). X 2. 

 Fig. 3. The intei-ior of a brachial valve. 

 Fig. 4. The muscular and deltidial area of the brachial valve ; showing the nari'ow, slightly thickened 



cardinal pi'ocess (j), the large crural plates and the quadripai'tite impression of the adductor 



muscles. X 2. 

 Fig. 5. The exterioi' of a brachial valve. 

 Figs. 6. 7. Cai'dinal and pi'ofile views of the same specimen. 



Fig. 8. Exterior of the pedicle-valve ; the area and delthyrium of the opposite valve showing. 

 Hudson River group. Cincinnati, Ohio. 

 For further illustration see Palaeontology of Ohio, Volume I, plate ix, fig. 4. 



Orthi.s sinuata, Hall. (?) (Compare O. Maria, Billings.) 



Fig. 9. A view of the brachial valve and profile of a specimen doubtfully referred to this species. 



Hudson River group. , Ohio. 



Fig. 10 = 19, by error. 



Orthis occidbntalis, Hall. (?) 



Figs. 11, 12. Views of a small specimen with coarse, simple plications, and the median sinus incipiently 

 developed ; probably the young of this species. 



Hudson River groiip. Savannah, Illinois. 



Orthis insculpta, Hall. 



Fig. 13. The interioi' of a pedicle-valve ; showing the muscular, vascular and ovarian markings. X 2. 

 Hudson River group. Oxford, Ohio. 

 For further illustration see Palseontology of Ohio, Volume I, plate ix, tig. 1. 



PL^SIOMYS, NOM. NOV. 



Page ISIS. 



Orthis reteorsa, Salter (= 0. Carleyi, Hall). 



Fig. 14. The interior of a pecicle-valve ; showing the short dental lamellje, subquadrate musculai- area, 



the vascular and ovarian makings. 

 Fig. 15. A view of the pedicle-valve of the orignal specimen ; showing the high area and i-etrorse beak of 



this valve. 

 Fig. 16. Profile of a large individual ; showing the great convexity of the brachial valve and the degree of 

 resupination of the beak of the pedicle-valve. 

 Hudson River group. Oxford, Ohio. 

 For further illustration, see Paleontology of Ohio, Volume I, plate xi, fig. 7. 



Orthis subquadrata, Hall. 



Fig. 17. The interior of the jjedicle-valve ; showing the component scars of the subquadrate muscular area, 



the lateral ovarian areas and the vascular impressions over the pallial region. 

 Figs. 18, 19. Brachial and cardinal views of a normal individual. 

 Hudson River group. Oxford, 'Ohio. 

 For further illustration, see Palaeontology of Ohio, Volume I, plate ix, fig. 2. 



