THE GENUS PTERYGOTUS 173. 
by an oval pointed tail. The whole surface is covered by the scale- 
like markings before mentioned as ornamenting the head. Professor 
M‘Coy, to whom I owe these notes on the general structure, has 
kindly furnished me with a restoration of the entire animal (fig. 543), 
which he believes to be closely allied to the great Aurypterus before 
mentioned, if not of the very same genus, and moreover of the same 
family as the living king crab or Lmeulus.” 
The restorations exhibit, in figs. 542, 543, 544, the chele fitted 
on to the ends of the mutilated ectognathary palp, in accordance 
with Agassiz’s idea of their position; while in fig. 543, the 
epistoma is represented as the carapace, and a transversely elon- 
gated eye is made to appear on either side of its median lobe, 
about midway between the middle line and the margin! The 
chelate appendages are made to arise from behind this supposed 
carapace, and are succeeded by two or three pairs of articulated 
appendages. In short, wherever Professor M‘Coy departs from 
M. Agassiz’s conception of the structure of Prerygotus, the alteration 
is not an improvement. 
In 1852 Mr. Salter published a “ Description of the Prerygotus 
problematicus,’ in the “ Quarterly Journal of the Geological Society,” 
in which the following passage occurs :— 
“Tt is probable that there are numerous species of the genus in 
the old rocks. Fragments, with the characteristic markings, occur 
in Upper Silurian shale at Gaspé, Lower Canada ; and portions of the 
limbs of a Bohemian species have been figured by the late M. Corda 
as the feet of Brontes, a genus of Trilobites.” 
Mr. Salter expresses his concurrence in the systematic views of 
Professor M‘Coy. 
The Report of the British Association for 1855, “ Transactions of 
the Sections” (pp. 89-91), contains the abstract of a paper by 
Mr. D. Page, “On the Prerygotus and Pterygotus Beds of Great 
Britain.” The following passages show what views were then 
entertained by Mr. Page with respect to the structure of these 
animals :— 
“The Pterygotus, of which there appeared to be three distinct 
species,—the gigantic prodlematicus, the anglicus, and the punctatus, 
—was altogether different in its general structure from any crustacean 
living or extinct. The portions chiefly found (and of these capital 
specimens are in the collections of Lord NKinnaird, the Watt 
Institution, Dundee, &c., all originally from Balruddery,) were 
the frontal cephalic shield, the posterior cephalic or thoracic shield, 
with its lunar-like epimera, the abdominal segments, generally from 
