CRUSTACEA. 91 



Dimensions. Of this species but two individuals retaining the parts in 

 juxtaposition have been observed, although detached portions of the bod} 

 are not of uncommon occurrence. Both of the entire example- are more or 

 less enrolled, the better preserved specimen having approximately the fol- 

 lowing dimensions: 



Body. I '' -| 'i Thorax. Pygidium. 



Length 36 mm. TO mm. 18 mm. 8 mm. 



Width 20 mm. 20 mm. 16 nun. L2 mm. 



Observations. Proitus 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. 



Proetus angustifrons. 



PLATE XX, FIGS. 1-;,; an-i, PLATE XXII, PIGS. 1-.".. 



Proitus angustifrons, Hall. Descr. New Species of Fossils, etc., p. 70. L861. 



Pro, tus angustifrons, Hall. Fifteenth Kept. N. V. state Cab. Nat. Hist., p. 98. 18H2. 



Proitus angustifrons. Hall. Illustrations of Devonian Fossils, pi. xx.. 6gs. I !. 7 1876. 



Our knowledge of this species is limited to portions of the cephalon 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 



