NO. 2297. BRACHIOPOD GEXUS PLATYSTROPHIA—McEWAN. 425 



This species is spiriferoid, much extended on the hinge. The 

 brachial valve is strone;!}^ ventricose; the slopes are inflated to such 

 a degree that the fold rises but slightly above the general convexity. 

 The pedicle valve is less convex than the brachial valve. The slopes 

 are compressed and the inner edges are elevated. This gives a thin 

 appearance to the shell near the cardinal angles and adds to the 

 depth of the conspicuous sinus. There are four j^lications on the fold 

 and tlu"ee in the sinus which are of about equal strength. The 

 slopes are occui^ied by about 13 or more closely spaced plications. 

 The cardinal areas of both valves are strong and broad. The beaks 

 are strongly incurved. 



This species has conspicuous gerontic characters. The convexity 

 is so great that it may equal or exceed the height. The shell is 

 thickened centrally and anteriorly to such a degree that the space 

 occupied by the soft parts is exceedingly small when compared with 

 the size of the shell. Both valves are marked by strong growth 

 lines which in the early ephebic stage run out to the cardinal extremes 

 and are closely spaced. 



Mr. Conrad reported the Silurian of the Falls of the Ohio as the 

 locality from which his types were collected. Mr. Meek * recognized 

 that his figures were - in agreement with specimens from Richmond, 

 Indiana. Mr. S. S. Lyon, of Jeffersonville, Indiana, who was 

 familiar with the paleontology of that locality, reported that he had 

 never found such a shell in that area. Mr. Meek sent the Richmond 

 specimens to Mr. Conrad and he identified them as the same as he 

 had figured under the name Delthyris acutilirata. 



Measurements, — 35.5 mm. along the hinge line, 27 mm. wide across 

 the middle, 18.2 mm. high, 20.8 mm. thick, 13.3 mm. sinal width, 11 

 mm. sinal depth, 4 mm. fold height. 



Occurrence. — Richmond group: Whitewater formation: Richmond, 

 etc., Indiana; Oxford and Dayton, Ohio; North Carolina and Louis- 

 ville R. R. between Wauhatchie and Hooker, Tennessee. Fernvale 

 limestone: Savannah and Wilmington, Illinois. Maquoketa shale: 

 Delafield, Wisconsin. 



Plesioty pes. —C&i. No. 48606, U.S.N.M. 



PLATYSTROPHIA ACUTILIRATA PROLONGATA Foerste. 

 Plate 45, fig. 22. 



Platystrophia acutilirata, Ci mings Amer. Joiirn. Sci., ser. 4, vol. 15, 1903, p. 35, 

 fig. 18 (part); 32nd Ann. Kept. Dept. Geol. Nat. Res. Indiana, 1908, pi, 35, 

 figs. 36, c, d. 



Platystrophia acutilirata prolongata, Foerste, Bull. Sci. Lab. Denison Univ., 

 vol. 16, 1910, p. 67, pi. 3, figs. 8a-b. 



One of the conspicuous variations of FJatystrophia acutilirata. is 

 represented by specimens which have elongated hinge lines and a 



» Meek, Pal. Ohio, vol. 1, 1873, p. 119, pi. 10, fig. 5. 



