PLATE Va. 
(Figures 2, 4, 16-21, 24-40 by E. Emmons ; 1, 3,5-14 by K. P. Whitfield; 15 by F. B. Meek; 22 by Philip Ast ; 
23 by J. C. McConnell.) 
Legend. A- Deltidium. 
j. Cardinal process, 
fp. Crural plate, 
t. Teeth, 
b. Sockets. 
a. Anterior adductor impressions. 
Posterior adductor impressions, 
r. Diductor muscular impressions, 
p. Pedicle-muscular impression, 
o. Ovarian impressions, 
v. Vascular markings. 
HEBERTELLA, nom. nov. 
Page 198. 
Orthis sinuata, Hall. 
Fig. 1. The interior of a pedicle-valve; giving the character of the muscular area, ovarian and vascular 
markings. 
Fig. 2. An enlargement of the muscular area of the pedicle-valve ; showing the large diductor ( r ), lineal 
central adductor (a) and the pedicle-scar ( p ). X 2. 
Fig. 3. The interior of a brachial v alve. 
Fig. 4. The muscular and deltidial area of the brachial valve; showing the narrow, slightly thickened 
cardinal process (j); the large crural plates and the quadripartite impression of the adductor 
muscles. X 2. 
Fig. 5. The exterior of a brachial valve. 
Figs. 6. 7. Cardinal and profile 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. 
Orthis sinuata, Hall. (?) (Compare 0. 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 occidentalis, 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 group. Savunnah, Illinois. 
Orthis insculpta, Hall. 
Fig. 13. The interior of a pedicle-valve.; showing the muscular, vascular and ovarian markings. X 2. 
Hudson River group. Oxford, Ohio. 
For further illustration see Palaeontology of Ohio, Volume I, plate ix, fig. 1. 
PLiESIOMYS, nom. nov. 
Page 196. 
Orthis retrorsa, Salter (= O. Carleyi, Hall). 
Fig. 14. The interior of a pecicle-valve; showing the short dental lamellae, subquadrate muscular area, 
the vascular and ovarian makings. 
Fig. 15. A view of the pedicle-valve of the orignal specimen ; showing the high area and retrorse 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 Palaeontology of Ohio, Volume I, plate xi, fig. 7. 
Orthis subquadrata, Hall. 
Fig. 17. The interior of the pedicle-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. 
