CRUSTACEA. 
91 
Dimensions. Of this species but two individuals retaining the parts in 
juxtaposition have been observed, although detached portions of the body 
are not of uncommon occurrence. Both of the entire examples are more or 
less enrolled, the better preserved specimen having approximately the fol¬ 
lowing dimensions; 
Body. Cepbalon. Thorax. Pygidium. 
Length_ 36 mm. 10 mm. 18 mm, 8 mm. 
Width__ 20 mm. 20 mm, 16 mm, 12 mm. 
Observations. Proetus Conradi is a well-defined species, approximating how¬ 
ever some of its associates, but readily diagnosed by its short, ovoid glabella 
and sloping pygidium, characters which are persistent and which serve to 
distinguish it from its nearest ally, Pr. angustifrons. 
Distribution. Upper Helderberg group; In the Schoharie grit at Schoharie, 
Schoharie county, and near Clarksville, Albany county. 
Pkoetus angustifrons. 
PLATE XX, PIGS. 1-5 ; AND PLATE XXII, FIGS. 1-3. 
Proetus angustifrons, Hall. Descr. New Species of Fossils, etc., p. 70. 1861. 
Proetus angustifrons, Hall. Fifteenth Kept. N. Y. State Cab. Nat. Hist., p. 98. 1862. 
Proetus angustifrons. Hall. Illustrations of Devonian Fossils, id. xx., figs. 1-4, 7. 1876. 
Our knowledge of this species is limited to portions of the cepbalon and the 
pygidium. 
The Cephalon appears to have been semicircular in outline, with a broad 
border slightly thickened near the marginal sulcus, and produced into short 
spines at the angles of the cheeks. 
The facial sutures are normal in their direction, crossing the frontal border 
very obliquely. 
Glabella elongate-sub-conate, tapering rapidly to a rounded, narrow ante¬ 
rior extremity, tangent to, but not encroaching upon the frontal margin. 
Length one-half greater than width. Surface depressed-convex, flattened 
above. Traces of three pairs of lateral furrows are faintly visible upon 
