EARLV DEVOXIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA I 35 



Proetus phocion Billings 

 (= P r o e 1 11 s c o n r a d i H all ?) 



Plate 9, figures 14-16 



Proetus phocion Billings. Palaeozoic Fossils v. 2, pt i. 1874. p. 63, fig. 3 > 

 Proetus phocion Hall & Clarke. Palaeontology of New York. 1888. 7:1^^, 

 pi. 25, fig. 9-10 



This .species, common in the Grande Greve limestone, was described 

 from an internal cast of an entire individual and this specimen was redrawn 

 bv Hall and Clarke and another enrolled individual fitrured with it. Our 

 material has not afforded any specimens as good as those, hence we have 

 here reproduced the drawings given in the last cited work. 



The original description was as follows: 



Description. 01)long-ovate; both extremities uniformly rounded, the pygidium more 

 broadly so than the head; sides of the thorax parallel. The head is rather strongly convex, 

 semi-elliptical; its length a little greater than half its width at the base; front smoothly 

 rounded; sides gently curved; posterior angles with very short spines. The marginal 

 border is well developed; it has a shallow median groove which is most distinct around 

 the front, and down the sides, but dies out on approaching the posterior angles of the 

 head; the border is separated from the cheeks by a distinct groove, which runs all around 

 the sides and front of the head, touching the front of the glabella in specimens with the 

 crust preserved. When the crust is not preserved, the front of the glabella, as seen in the 

 cast, does not quite reach the cast of the groove. Glabella regularly conical, about one 

 seventh shorter than the head, convex, most elevated between the eyes. There are indica- 

 tions of glabellar furrows, but they are too indistinctly seen in the specimens to be located 

 with certainty. Neck-furrow crossing the glabella, very nearly on (but a little behind) a 

 line connecting the posterior corners of the eyes. It is nearly straight for about one half 

 of its length in the middle, and then turns forward, slightly, at each end to the eye. The 

 neck-segment has a small tubercle in the middle and at each end is partially cut off, by a 

 short groove which extends downwards and outwards from the neck-furrow; the part 

 above the groove having somewhat the appearance of a large triangular tubercle. Eyes 

 large, semi-circular, in contact with the sides of the glabella. 



Thorax of ten segments; axis rather strongly convex; about as wide as the lateral 

 lobes. Pleurae geniculated at an obtuse angle, at a little less than half their length from 

 the axial furrows; strongly facetted in the outer half. Pleural groove most distinctly 

 impressed about the mid length of the pleurae, not reaching the outer extremities. 



Pygidium not so convex as the head; nearly semi-circular; a narrow convex border 

 all around the sides and posterior extremity; axis conical, extending to the marginal border. 

 There are ten or eleven segments in the axis, and six or seven (each with an obscure median 

 groove) in the side lobes. 



Length of an entire specimen, seventeen lines; width, eleven lines; length of head, 

 six lines; of the thorax, seven lines; of the pygidium, five lines. 



It would be difficult to establish a difference between P, phocion 

 and P. CO n rad i Hall ' and there is none between the Gaspe trilobite and 



' See Palaeontology of New York. 1888. 7 : 89, pi. 20, fig. 9; pi. 21, fig. 27, 28; pi. 

 22, fig. 4. 



