I'latystropllia biforata.l 
BRACHIOPODA. 
Platystrophia biforata Schlotheim, sp. 
PLATE XXXIIl, FIGS. 40-52. 
1820. Terebratulites biforalus Schlotheim. Petrefactenkunde, p. 26.5. 
For other European synonomy see Davidson's Monograph of T'>ritish Silurian Brachiopoda, pt. vii, 
p. 268, 1860-1871. 
1843. Spirifer sheppardi Castlenau. Essai sur le Systeme Silurien Septentrionale, p. 42, pi. xiv, 
fig. 15. 
1843. Delthyris brachynota Hall. Geology of New York; Report Fourth District, p. TO, fig. 6, 
1844. Orthis and Delthyris Owen. Geological Exploration of Iowa, Wisconsin and Illinois, pi. xv, 
flgs. 3, 7. 
1847. Delthyris lynx Hall (partim) (non Eichwald). Palueontology of New York, vol. i, p. 133, 
pi. XXXIID, flg. 1. 
1852. Spirifer biforatus, var. lynx Hall. Ibidem, vol. ii, p. 65, pi. xxii, llg. 1. 
1856. Orthis biforata Billings. Canadian Naturalist and Geologist, vol. i, p. 206, Ilgs. 6 -10. 
1863. Orthis lynx Billings. Geology of Canada, p. 167, fig 149. 
1865. Platystrophia regularis Shaleu. Bulletin of the Museum of Comparative Zoology, p. 67. 
1873. Orthis (Platystrophia) biforata Meek. Palaeontology of Ohio, vol. i. p. 112. 
1874. Orthis biforata Nicholson and Hinde. Canadian .Journal, vol. xiv, p. 158. 
1875. Orthis lynx Miller (partim). Cincinnati Quarterly Journal of Science, vol. ii, p. 2b. 
1875. Orthis biforata White. Report of the U. S. Geographical Survey west of the 100th Meredian, 
vol. iv, p. 74, pi. IV, fig. 9. 
1883. Orthis (Platystrophia) biforata, var. lynx Hall. Second Annual Report, New York State 
Geologist, pi. XXXV, flgs. 11-14 (not flgs. 9, 10, 15 of pi. xxxv, and 
fig. 30 of pi. xxxiv=P. biforata, var. lynx). 
1885. Orthis biforata, var. lynx, forma reversata and daytonensis Foerste. Bulletin of the Denison 
University, vol. i, pp. 81, 82, pi. xiii, flgs. 7, 8. 
1889. Orthis biforata Netteli;oth. Kentucky Fossil Shells, p. 35, pi. xxix, flgs. 18-29. 
1890. , Orthis biforata Foerste. Proceedings of the Boston Society of Nat. Hist., vol. xxiv, p. 312. 
1892. Platystrophia lynx Hall. Palaeontology of New York, vol. viii, pp. 202, 223, pi. vB, flg. 10. 
Description: Since the original description of this species is not accessible, that 
by Davidson {op. cit. p. 269) is here reproduced: "Transversely semiellipbical or 
subquadrate, wider than long, more or less globose, the length, width and depth 
varying sometimes but little; hinge-line more often rather less than the width 
of the shell, sometimes slightly exceeding the general breadth, with short, acute 
mucronate wings, or rounded terminations; in front the ventral valve is abruptly 
deflected and indents the opposite one; beaks in both valves much incurved and 
approximating. Ventral valve convex, with a wide, deep medial sinus, commencing 
at the extremity of the beak and widening as it nears the front. Area triangular 
of moderate hight, fissure [delthyrium] open, beak angular, incurved. Dorsal valve 
deeper than the opposite one, at times gibbous, with a wide longitudinal fold, com- 
mencing at the extremity of the umbonal beak and extending to the front; area a 
little less wide than in the opposite valve, [erect], fissure [delthyrium] open. Surface 
of both valves ornamented with a greater or lesser number of radiating triangular 
ribs; of these from one to five (and in some varieties more) [in American forms 
usually three] furrow the medio-longitudinal sinus, while from two to six or seven 
[usually four in this country] compose the mesial fold. The valves are also crossed 
at intervals by numerous concentric, raised, subimbricating lines; the surface is also 
marked with small punctures [in well preserved specimens the surface is crowded 
