CRUSTACEA 
99 
Dimensions. An average individual affords the following measurements; 
Body. Cephalon. Thorax. Pyg-idiinn. 
Length_ 43 mm. 16 mm. 14 mm. 13 mm. 
Width_ 23 mm. 23 mm. 23 mm. 21 mm. 
The largest pygidium observed has a length of 22 mm. and a width of 35 
mm., the smallest a length of 9 mm. and a width of 15 mm. 
Distribution. In the sandstones at Pendleton, Indiana, associated with the 
preceding species. 
Proetus crassimarginatus. 
PLATE XX, FIGS. 6-8, 20-31 ; PLATE XXII, FIGS. 20-26 ; AND PLATE XXV, FIG; 8. 
Calymene crassimarginatus. Hall. Geology of N. Y., Survey of Fourth Geol. Dist., p. 172, tig. 5. 1843. 
Pro'elus crassimarginata, Hall. Twelfth Kept. N. Y. State Cab. Nat. Hist., p. 88. 1859. 
Phillipsia crassimarginata, Billings. Canadian Journal, p. 362. 1861. 
Proetus crassimarginatus. Hall. Descr. New Species of Fossils, etc., j). 72. 1861. 
Proetus crassimarginatus. Hall. Fifteenth Rept. N. Y. State Cab. Nat. Hist., p. 100. 1862. 
Proetus crassimarginatus, Hall. Illustrations of Devonian Fossils, pi. xx, tigs. 20-31. 1876. 
Proetus Co7tracli, Hall. Illustrations of Devonian Fossils, pi. xx, tigs. 5, 8, 9. 1876. 
General Form and Proportions. Body regularly ovate, margins evenly 
tapering from the base of the cephalon to the narrow posterior extremity. 
Length to width at base of cephalon, as 2 to 1. 
Surface convex and strongly trilobate. 
Cephalon semicircular in outline, border broad, strongly recurved in front,’ 
more depressed and flattened at the sid'es, and produced at the genal angles 
into a broad, flat spine. Length to width as 1 to 2. 
Facial Sutures normal. 
Glabella large, sub-quadrate, semi-ovoid, narrowing slightly toward the 
anterior extremity; length equal to five-sixths the length of the cephalon, 
and width more than one-third that of the cephalon. Surface very convex, 
slightly flattened above; sides rising abruptly from the shallow marginal 
furrows. External evidence of the lateral furrows wanting. A single speci¬ 
men from which the test has been so far weathered as to leave only a thin 
film near the lower surface, shows four pairs and the accessory furrows, of the 
