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PALEONTOLOGY OF NEW YORK. 
aniiulation of the pygidium. The surface of the hypostoma is punctate and 
covered with strong, concentric, lamellose markings. 
Dimensions. An average individual affords the following measurement; 
Body. Cepliiilon. Thorax. Pygidium. 
Length_ 36 mm. 14 mm. 12 mm. 10 mm. 
Width_ 22 mm. 22 mm. 20 mm. 18 mm. 
The smallest entire specimen observed has a length of 12 mm., and a 
width of 9 mm., and the largest specimen, in which the parts are somewhat 
detached, was an individual measuring 62 mm. in length. 
Observations. Proetus Rowi is one of the rarer species of the Hamilton fauna. 
The fossil was first brought to public notice by Mr. Le Row, in the Poughkeepsie 
Telegraph of November 22, 1837, and was described by Green in the following 
year, as cited. The original was from the sandy shales of the group in Otsego 
county. In one locality only has it proven to be an abundant fossil in good 
preservation, namely, on Seaver’s creek in the township of Canandaigua, Ontario 
county, in the shales and limestone immediately overlying the Marcellus shales. 
Careful comparison of this species with Proetus darns, Hall, of the Upper 
Helderberg limestone, shows a very close similarity in the broader features and 
in the general expression of the animal. While the former may be regarded as 
the Hamilton representative or descendant of the latter, there are certain asso¬ 
ciated details which will serve to distinguish the species. Proetus Rowi has larger 
eyes, flatter thoracic segments, a less abruptly tapering axis and a larger num¬ 
ber of annulations upon the pygidium, and a peculiar ornamentation upon the 
cheeks, thorax and pygidium, which has not been noticed in Proetus darns. 
Proetus marginalis. 
Calymene marginalis, Conrad. Ann. Kept. Palaeontology of N. Y., p. 66. 1839. 
Proetus margmalis (?), Hall. Desci'. New Species of Fossils, etc., p. 76. 1861. 
Proetus marginalis (1), Hall. Fifteenth Kept. N. Y. State Cab. Nat. Hist., ii. 104. 1862. 
Proetus marginalis (?), Hall. Illustrations of Devonian Fossils, pi. xxi, figs. 24-28. 1876. 
The original of Mr. Conrad’s Calymene marginalis was a cejihalon described 
by him in the following terms {loc. at .); 
