552 Systematic Paleoxtology — Upper Devonian 



which differ on cardinal extremities of ventral valve from those on re- 

 mainder of shell. 



Interior of ventral valve with diverging flabelliform scars for diductor 

 muscles, the surface of which is plicate. Adductor muscular scars dis- 

 tinct, divided by an impressed line. Interior of dorsal valve pustulose 

 with well-marked scars for attachment of adductor muscles and a forked 

 cardinal process which is seen in cast as two circular pits. 



Length 25 mm.; width 75 mm. 



Occurrence. — Jennings Formation, Chemung Member. Town 

 Creek, 3398. 



Collection. — Marjdand Geological Survey. 



Genus LEPTOSTROPHIA Hall and Clarke 



Leptostrophia perplana var. nervosa (Hall) 

 Plate XLVIII, Figs. 1-4 



Strophomena nervosa Hall, 1843, Geol. of N. Y., Rept. 4th Dist., p. 266, 



fig. 1. 

 Stropheodonta perplana var. nervosa Hall, 1S67, Pal. of N. Y., vol. iv, p. 13, 



pi. xix, figs. 13-16. 

 Leptostrophia perplana var. nervosa Hall and Clarke, 1892, Pal. of N. Y. 



vol. viii, pt. 1, p. 15, figs. 14, 15, 17. 



Description. — Shell very depressed, subplane, gently convexo-concave 

 in the umbonal region. Surface covered with fine radial strife which are 

 irregularly thickened and give the surface a rough and scraggy ap- 

 pearance. These plications are normally of different orders of size, 

 between each two of equal size there being 3-5 of lesser size, a mode of 

 arrangement of surface markings which is a very ancient feature among 

 these brachiopods. Individuals of this variety show^ a tendency to irregu- 

 lar thickening of the plications at early growth stages, but in the occasional 

 individual in which it is not well displayed at maturity there is a notable 

 irregularity in the course of the striae. 



The hinge is denticulate and the deltidium very narrow, almost or 

 wholly closed. On the interior the ventral valve presents very broad 

 flabcllate muscle scars surrounded by a papillose pallial surface. In the 



