LF2 ON THE ANATOMY AND AFFINITIES OF 
Old Red of Scotland. I have conferred upon this species the name 
of Pterygotus anglicus, which at once suggests its origin and the 
singular view which was once entertained as to its nature.” 
Although the parts figured by M. Agassiz have, as I have taken 
occasion to point out in successive notes, in no single case the nature 
attributed to them, his sagacious indication of the affinities of 
Prerygotus deserves thankful recognition. 
The views of Professor Agassiz respecting the affinities of 
Pterygotus are adopted and expressed still more strongly by M. von 
Eichwald, in his Memoir on the Grauwacke of Livonia and Esthonia.! 
“Tt appears at first sight,” says he, “that this (Pzerygotus) was a 
colossal Eurypferus, at least the genera are very closely allied.” 
M. von Eichwald differs from Agassiz only in considering the latter’s 
“caudal segment” to have been thoracic. His specimen, which he 
ascribes to P. anglicus, was found in the Limestones of Rootsikiille. 
In the “ Annals and Magazine of Natural History” for 1849, series 
2, vol. iv. pp. 393, 394, Professor M‘Coy gives an account of the remains 
of a new species of Plerygotus, P. leptocheles. In his preparatory 
remarks, Professor M‘Coy erroneously states that Agassiz has “in his 
work on the Fishes of the Old Red Sandstone referred it (Pterygotus) 
to the Extomostraca, without indicating any particular division.” The 
fact being, as is proved by the quotation just given, that he does not 
consider Pterygotus to be entomostracan at all, but to be intermediate 
‘between “ 77zlobites and Entomostraca.” 
Following Agassiz and Eichwald, Professor M‘Coy indicates the 
close relations which obtain between Péerygotus and Eurypterus ; 
but he unites Plerygotus, Eurypterus, and Bellinurus, and makes 
of therm a family of the Pecilopoda. Professor M‘Coy considers 
that he has found evidence of the existence of more than one pair of 
didactyle feet. 
Professor M‘Coy’s views are further expressed in the restored 
figures of Pterygotus, which he has furnished to the fifth edition of 
Sir Chas. Lyell’s “ Manual” (1855), and in the following passage of 
that work (p. 420) :— 
“ The carapace of this huge crustacean, which must have rivalled, 
if not exceeded in size, the largest crab, is furnished at its hind 
part with two short prongs, and has two large eyes near the 
middle, much like those of the Eurppterus found in the coal- 
formation of Glasgow. The body consists of ten or eleven movable 
rings (the exact number is not ascertained), and was terminated 
1 Die Grauwacke Schichten von Liy- und Esth-land, von Ed. von Eichwald. Bulletin 
de la Société Impériale des Naturalistes de Moscou. 
