BRACHIOPODA. 

 Pliftystrophia biforata.l 



PLATYSTROPHIA BIFORATA Schlotheim, sp. 



PLATE XXXIII. PIGS. 49-52. 



1820. Terebratulites biforatus SCHLOTHEIM. Petrefactenkunde, p. 265. 



For other European synonomy see Davidson's Monograph of British Silurian Brachiopoda, pt. vii, 



p. 268, 1866-1871. 

 1813. Spirifer xheppardi CASTLENAU. Essai stir le Systeme Silurien Septentrionale, p. 42, pi. xiv, 



flg. 15. 



1843. Delthyris brachynota HALL. Geology of New York; Eeport Fourth District, p. 70, tig. 6 



1844. Orthis and Delthyris OWEX. Geological Exploration of Iowa, Wisconsin and Illinois, pi. xv, 



figs. 3, 7. 

 1847. Delthyris lynx HALL (partim) (non EICHWALD). Paheontology of New York, vol. i, p. 133, 



pi. XXXIID, rig. 1. 



1852. Spirifer biforatus, var. lynx HALL. Ibidem, vol. ii, p. 65, pi. xxn, Ug. 1. 

 1856. Orthis biforata BILLINGS. Canadian Naturalist and Geologist, vol. i, p. 206, tigs. 6-10. 

 1863. Orthis lynx BILLINGS. Geology of Canada, p. 167, fig 149. 

 1865. Platystrophia regularis SHALEH. 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. 25. 



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 rigs. 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. xm, flgs. 7, 8. 



1889. Orthis biforata NETTELKOTH. 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. vili, 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 semielliptical 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 



