66 
ee 
The beak of the ventral valve is small, prominent, and slightly incurved; the area of 
moderate width, and sometimes with a smooth triangular space occupying the place of the 
foramen, The dorsal area narrow. 
The surface is marked with ‘‘ numerous crowded striz, about nine or ten of which are 
niuch stronger and more elevated on the umbo of the ventral valve, with finer ones coming in 
between and on either side; strize frequently increasing by intercalation and bifurcation, until 
they become very numerous and much finer at the margin. On the dorsal valve, the striz 
are similar to those of the ventral valve ” (Hall). 
According to the observer just quoted, “the interior of the ventral valve, and casts of 
the same, show a large flabelliform divaricator muscular impression, which is somewhat widely 
separated in front, and each division distinctly lobed. The occlusor muscular impressions 
occupy a semi-elliptical space on each side of a narrow central depression, the marking on 
either side being double in well preserved specimens. The upper extremities of this im- 
pression are close under the arch of the umbo, and separated by a smooth space from the 
divaricator impressions. Beyond the muscular impressions, the interior surface is minutely 
pustulose, the points being more prominent just without their limits; beyond which the 
course of the vascular impressions can be distinctly traced. In the dorsal valve the anterior 
and posterior occlusor muscular impressions are very conspicuous and deeply marked, and 
often limited by an elevated ridge, a narrow longitudinal ridge dividing the two pairs. On 
each side, and below the muscular impressions, the surface is marked by small pustules or 
tubercles; and beyond these the surface is minutely pustulose, the vascular impressions be- 
coming distinct towards the margin. The cardinal process is divided from the base, the 
divisions strongly diverging.” (Pulwontologg of New York, Vol. IV, p. 103. 
S. demissa, like the preceding, belongs to the section elevated by Hall to the rank of 
a genus under the name of Strophodonta. It is a variable species, and unless the hinge-line 
be preserved with the area, it is not alwys possible to refer examples to it with certainty. 
‘The species occurs in almost every sub-division of the Devonian series of North America. 
Locality and Formation.—Corniferous Limestone of Port Colborne and of numerous other 
localities in Western Ontario, 
78. STROPHOMENA INEQUISTRIATA (Conrad). 
Strophomena inequistriata (Conrad), Journal Acad. Nat. Sciences, Philadelphia, Vol. 
VIII., p. 254, Plate XIV. Fig. 2. , 
Strophomena inequistriata (Hall), Geol. Rep. 4th District, p. 200, Fig. 4; and Tenth 
Report on the State Cabinet, p. 142. 
Strophomena inequistriata (Billings), Journal Canadian Institute, New Series, Vol. VI1., 
. 338. 
R Strophodonta inequistriata (Hall), Pal. New York, Vol. IV., p. 106, Plate XVIII, Figs. 
2a—k. 
[Compare Orthis interstrialis (Phillips), Pal. Foss. p. 61, Plate XXV. Figs. 103 a-d; 
Leptena interstrialis (Davidson), Brit. Fossil Brachiopoda, p. 85, Plate XVIII., Figs. 15-18 ; 
Strophodonta varistriata, var. arata (Hall), Pal. New York, Vol. IIL, p. 183, Plate 18, Figs. 
la-i; Stophodonta textilis (Hall), Pal. New York, Vol. IV.,p. 108, Plate XVIII. Fig. 3; 
and Strophodonta concava (Hall), Pal. New York, Vol. IV., p. 96, Plate XVI.| 
Shell semi-oval or semi circular, widest at the hinge-line, which varies from one to three 
inches in length. Cardinal angles usually somewhat acute, and sometimes eared. Width of 
the shell usually from a fourth to a third greater than the length. Valves concavo-convex ; 
the ventral valve convex, with a variable curvature, often abruptly arched towards the margin ; 
the dorsal valve concave, but generally Jess strongly curved than the ventral. Beak of the 
ventral valve apparently very variable in its prominence ; the area narrow, vertically striated, 
and crenulated in the neighbourhood of the beak. 
Surface marked with distant elevated simple striz, which increase towards the margins 
of the shell by interstitial additions, and which are separated by flat or slightly concave inter- 
spaces, distant from half a line to a line at the margin. These interspaces are occupied by 
exceedingly fine and close longitudinal strive, from four to eight existing in one interspace. 
Further, the coarse and fine radiating strize are cancellated by a crowded series of exceedingly 
fine and cl se-set concentric strize. 
