22U CONTRIBUTIONS TO CANADIAN PALAEONTOLOGY. 



Strophodonta perplana, Conrad. 



Strophomcnu perplana, Conrad. 1842. Joiirn. Ac. Nat. Sc. Phil, vol. VIII, p. 2.57, 



pi. xiv, fig. 11. 

 Siroplwmena pluristriata, Conrad. lb., p. 259. 

 Strophornena deUhijris, Conrad. lb., p. 258, pi. xiv, fig. 19. 

 Stro-phomcna crenistria, Hall. 1843. Eep. Fourth Geol. distr. N. Y., p. 171. 



" nrrrosa, Hall, lb., p. 260, fig. 1. 



Slroplioilonta fragilis, Hall. 1857. Fourth Reg. Rep. N. Y. State Cab. Nat. Hist., 



p. 143. 

 iStropltodonta fragilis, HaXl 1858. Geol. Iowa, vol.1, pt. 2, p. 496, pi. iii, figs. 



G a-c. 

 t^itrophomi itu pjcrplana, Billings. 1861. Can ad. Journ., N. S., vol. VI, p. 343. 

 Strophodonta perplana. Hall. 1867. Pal. N. Y., vol. lY, pp. 92, 98 and 113, pis. 



xi, xiii, xvii. and xix. 



Siropliomenu perplana, Nicholson. 1873. Pal. Ontario, p. 64, figs. 20a, a. 



Strophodonta perplana, "\Yalcott. 1884. Pal. Eureka distr. Nevada, p. 120, pi. 

 xiii, figs. 11. 



Strophodonta iicrplana, var. TulUensin, (?) H. S. Williams. Bull. Geol. Soc. Am., 

 May, 1890, p. 493, pi. xii, figs. 1-4. 



Peace Eiver, at Vermilion Falls, R. (r. McOounell, 1SS[»: a nearly 

 perfect and well preserved ventral valve, which resembles S. i^erplana, 

 var. Titlliensis, in the circumstance that each end of its hinge line is 

 produced into a short spine or mucronate point. It is, however, much 

 larger than the ligured t3'pe of that varietj^, and the mucronate jjoints 

 at its cardinal angles are proportionately shorter and not so slender. 



Prof. Williams (op. cit., p. 493) says that S. perplana •■ appears to 

 be an American type, and is seen with variations all through our 

 Do\'onian, but it is not described in the Aniei'ican Devonian." "In 

 the European race" (of the Strophodonta uui/quistriata tj-pe) "as we 

 reach the Cuboides /one, the terminations of the hinge develop into 

 slender mucronate points." " In the American race " (S. perplana) 

 " these mucj'onate points first appear in the Tully limestone, and are 

 characteristic of the race afterward till it ceases." Jlucronate lateral 

 extensions of the hinge line, however, occur in the Strophornena Leda 

 of [jillings,* from the Silurian rocks at Anticosti, and in an undescribed 

 species of Strophornena recently collected by Mj'. .T. B. Tyrrell from 

 rocks ol' about the same age on the east side of Lake Winnipegosis, at 

 Cedar Lake and on the Saskatchewan, they are developed into exceed- 

 ingly long and slender spines. 



• (ieol. Siirv. Ciin;nl;i. Pahuozoic Fossils, vol. I., ,.. i2fl, ligs. 98, 99. 



