PLATE Vb. 



(Figures J, 4, 8, 15--J1, 'i7-;i'J, by 1{. 1'. Wuxtfielu; 9, 22-20, by Ji. Emmons; lu-14, by J G. McConnell.) 



Legend. A- Deltidium. a. Autei-ior adductor impi-essions. 



j. Cardinal process. a'. Posterior adductor impressions. 

 t. Teeth. r. Anterior diductor impressions. 



b. Sockets. !•'. Posterior diductor impressions. 



c. Ciura. 0. Ovarian markings, 

 s. Septum. V. Vascular markings, 

 p. Pedicle muscle. 



PLATYSTKOPHIA, King. 



Page 200. 



OiiTHis BiFORATA, Sclilotheini, var. LYNX, von Eichwald. 



Fig. 1. A cardinal view of an average individual ; showing the area and delthyrium of each valve. (The 



lines limiting the delthyrium are too strongly defined.) 

 Fig. 2. An exterior of tlie brachial valve of a smallei' specimen. 

 Fig. 'S. The interior of a brachial valve ; showing the narrow, linear cardinal process, large crural plates 



and the quadripartite impression af the adductor muscles. 



Fig. 4. The interior of a large pedicle-valve. The apical portion of the shell has been absorbed, being 

 the usual condition in old shells of this form, thus exposing the impre.ssion of the pedicle-muscle. 

 The specimen also shows the compact form of the musculai- scars, the vascular trunks and ova- 

 I'ian markings. 



Hudson River group. Cincinnati, Ohio. 



Okthis BIFORATA, Schlotheiiu, var. laticosta. Meek. 



Figs. 5, 6, 7. Profile, brachial and front views ; showing the high median fold characterizing this form. 

 Fig. 8. The interior of a brachial valve. 



Fig. 9. An enlargement of the delthyrial portion of the brachial valve. The obsolescent character of 

 the cardinal process is probably due, in part, to reabsorption. 

 Hudson Rivei- group. Cincinnati, Ohio. 



Orthis BIFORATA, Sclilotheiiii. 



Fig. 10. The exterior of the pedicle-valve. The surface is covered with fine granules which, however, are 

 very rarely retained (and almost never visible in ordinary specimens). X 3. 

 Trenton limestone. Trenton Falls, N. Y. 

 For further illustration of Plattsteophia, see Davidson, Silurian Brachiopoda, pi. xxxviii, figs. 11- 

 25 ; Palseontology of Ohio, Volume I, plate x. 



BILOBITES, LiNNE. 



Page 204. 



Orthis biloba, Liiuie. 



Figs. 11, 12, 13, 14. Views; showing tlie variation in form in this species. Fig. 14 is of the type described 

 by RiNGDEBERG as 0. acutiloba. X 3. 



Niagara group. Lockport, N. Y. 



Orthis varica, Comatl. 



Figs. 15, 16, 17. Three views of the same specimen. X 2. 



Fig. 18. The interior of the pedicle-valve ; showing the area, delthyrium, teeth and outline of the muscu- 

 lar area. X 4. 



Fig. 19. The interior of the brachial valve ; showing the cardinal process, the great crura, large muscular 

 area, and the pectinated surfaces of marginal contact. X 5. 

 Lower Helderberg group. Near Clar/csville. iV. Y. 



