106 
GEOLOGY OF THE FOURTH DISTRICT. 
2 and 2 b. Delthyris radiata. (Spirifer radiatus, M. C. t. 493. Silurian Researches , 
p. 624, pi. 13, f. 6.) — Semi-oval, ventricose, (often flattened from compression); shell 
covered with fine radiating striae, scarcely interrupted by lines of growth; extremities of the 
hinge line rounded ; area moderate ; perforation small. 
Fig. 2 is from the shale and somewhat flattened ; 2 b, is from the succeeding limestone and 
is more ventricose, not having been compressed. 
This shell, in its various phases, resembles too closely the figures, both in the Mineral 
Conchology and the Silurian Researches to be referred to any other species. The descrip¬ 
tion in the latter corresponds with our largest specimens. It ranges from the iron ore beds 
of the Clinton group to the Niagara limestone, but is more abundant in the shale of the latter 
group. 
Locality —Wolcott, Rochester, Lockport, and numerous other points. 
3 and 3 b. Delthyris staminea, n. s. (References. Spirifer crispus? Silurian System, p. 
624, pi. 13, f. 8. Delthyris crispa, Dalm. 1. c. p. 122, t. iii, f. 6; His. Pet. Suec., p. 73, t. 
xxi, f. 5.) — Semi-circular, lower valve very gibbous, and produced into an incurved beak, 
upper one moderately elevated in the centre ; ribs, commonly two in the upper, and three in 
the lower valve on each side the mesial fold, crossed by numerous elevated, thread-like lines ; 
beaks remote, extremities of the hinge line rounded; area large. Cast of shell smooth. 
This shell resembles the figure of Spirifer crispus ? ( Silurian Researches .) Hisinger’s 
figure differs from Murchison’s and is less like our shell. I have obtained casts of a shell 
very similar, if not identical with this one, from the “ coralline limestone,” below the water- 
lime at Schoharie. 
Locality —Common in the lower part of the shale at Lockport and Lewiston, less abundant 
at Rochester and Wolcott. 
4 and 4 a. Delthyris decemplicata, n. s. Sub-triangular, gibbous, ribs ten, finely striated 
longitudinally, and crossed by undulating imbricated lamellae, which are less prominent on the 
mesial fold; mesial fold of the lower valve deeply impressed toward the margin and elevated 
in front. 
This shell is distinguished from the last by the greater number of ribs, which are crossed 
by imbricated lamellae, while in D. staminea, these are simple elevated lines. From com¬ 
pression these two shells often approach each other in form. There are usually four ribs in 
the upper, and five in the lower valve, on each side the mesial fold. It much resembles 
Spirifer octoplicatus, M. C. t. 562, f. 2 and 3; but the surface is striated, the mesial fcld is 
not plain, but the lamellae are less prominent than on the ribs. 
Locality —Lockport and Lewiston, occurring with the last named species, and more abun¬ 
dantly. 
8. Delthyris sinuatus. (Terebratula sinuata, Sowerby in Linn. Trans. Vol. xii. p. 516, 
t. 28, f. 5 and 6; Delthyris cardiospermiformis, His. Antechn. Yol. iv. t. 7, f. 6. Dalm. sur 
les Terebratules, p. 124, t. 3, f. 7; His. Pet. Suec. p. 74, t. 21, f. 9. Spirifer cardiosper- 
