DEVONIAN FAUNAS. 305 
Brachial valve convex in the middle, depressed toward the margins, 
the beak produced but slightly beyond the hinge-line. Surface of 
both valves marked by fine, raised, radiating, irregularly-bifurcating 
strie, which are curved toward the cardinal margin; also by more or 
less conspicuous, concentric lines of growth. 
The dimensions of an average specimen are: length, 27 mm.; width, 
28 mm. 
Remarks.—This species is associated with R. oblata and resembles 
it in some respects, but is much less frequent. It has a relatively 
longer hinge-line, with a much larger cardinal area, and consequently 
a more prominent beak on the pedicle valve. The length of the shell 
is also usually greater, as compared with its width. 
DALMANELLA PERELEGANS (Hall). 
Plate XXXV., Figs. 5-8. 
See, also, p. 827. 
1859. Orthis perelegans Hall, Pal. N. Y., vol. IIL, p. 171, pl. 13, 
figs. 4-12. 
Description.—Shell transversely subelliptical in outline, the hinge- 
line about equal to one-half the greatest width. Pedicle valve strongly 
elevated along the median line from the beak towards the front, sloping 
laterally; the beak small, pointed, incurved over the narrow, concave, 
cardinal area, extending a little beyond that of the brachial valve. 
Brachial valve nearly or quite as convex as the pedicle valve, more 
or less flattened or depressed along the median line; beak small and 
but little produced beyond the hinge-line. Surface marked by fine, 
irregularly-bifurcating, radiating, raised strie, which are often ir- 
regularly alternating, several smaller ones occupying the spaces be- 
tween larger ones. ‘These radiating markings are crossed by con- 
centric lines of growth, of greater or less prominence. 
The dimensions of a full-grown specimen of average size are: 
length, 24 mm.; width, 27 mm.; thickness, about 12 mm. 
20 ; 
