20 DEVONIAN FAUNA. 



An American species, C. craspedota, Hall 1 , which lias much resemblance to it, 

 differs in having a narrower head and more oblique cheek-spines, besides having a 

 central neck-spine, and eyes which slant more backwards than in the English 

 species. 



2. Genus. — Proetus, Steininger, 1831. 



Founded for a Devonian Trilobite, P. Cuvieri, Stein., and others which had 

 formerly been included in Calymene, this genus is defined by being of an oval shape, 

 with entire borders, with large rounded eyes, and generally with ten thoracic 

 segments. It extends from the Lower Silurian to the Carboniferous. 



1. Proetus batillus, Whidborne. Plate I, figs. 23 — 26, and Plate II, figs. 1 — 4. 



1841. Calymene, sp., Phil. Pal. Poss., p. 230, pi. lviii, figs. 249 a, c (only). 

 1889. Proetus batillus, Whidb. Greol. Mag., dec. 3, vol. vi, p. 28. 



Description. — Cephalic shield wide, flattish, with thick dense test in two (or 

 three) layers, nearly semicircular in outline, with stout, straight, conical cheek- 

 spines sometimes of considerable length. Border large, prominent, and rounded, 

 marked with six or seven slightly sinuous ridges, continued on the cheek-spines. 

 Glabella flattened; in profile somewhat convex in front, straight behind; in 

 outline nearly square, rounded in front where it reaches the border, slightly 

 concave behind, with steep sides, minutely and closely granulated. Neck-furrow 

 linear, with a minute prominence at each extremity. Neck-lobe very broad, long, 

 and arched, showing numerous very fine transverse lines where the two outer 

 layers of test are removed. Lateral processes of the neck-lobe sloping back- 

 wards. Facial suture cutting the front border obliquely, thence extending close 

 to the glabella, and scarcely arched at the eye-lobe, turning outwards at the 

 marginal furrow of the cheek, and cutting the hind margin not far from the 

 glabella. Eye long, smooth, rounded, situated in the middle of the cheek close to 

 the glabella, bounded below by a linear furrow. Cheek beginning just in front of 

 the side part of the glabella, slightly tumid, bounded all round by a furrow which 

 is linear in front, and steep and excavated at the hind margin ; a similar but 

 shallower furrow round the eye. 



First segment of thorax granulated. 



1 1888, Hall, ' Geol. N. T.,' vol. vii, p. 148, pi. xxiv, figs. 15—20. 



