BRITISH FOSSILS. 7 



Eichwald, in his Memoir on the Grauwacke of Livonia and Esthoma.* 

 " It appears at first sight," says he, " that this (Pterygotus) was a 

 colossal Eurypterus, 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 Kootsikiille. 

 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 Pterygotus, P. leptocheles. In his pre- 

 paratory 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 Entomostraca, 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 " Trilobites and Entomostraca." 



Following Agassiz and Eichwald, Professor M'Coy indicates the 

 close relations which obtain between Pterygotus and Eurypterus ; 

 but he unites Pterygotus, Eurypterus, and Bellinurus, and makes 

 of them a family of the Pcecilopoda. 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. Ly ell'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 Eurypterus found in the coal- 

 formation of Glasgow. The body consists of ten or eleven 

 moveable rings (the exact number is not ascertained), and was 

 terminated 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 Eurypterus before mentioned, if not of the 

 very same genus, and moreover of the same family as the living 

 king crab or Limulus." 



The restorations exhibit, in figs. 542, 543, 544, the chelae fitted 

 on to the ends of the mutilated ectognathary palp, in accordance 



* Die Grauwacke Schichten von Liv-und Esth-land, von Ed. von Eichwald. Bulletin 

 de la Socic-te Imperiale des Naturalistes de Moscou. 



