24 BRITISH FOSSIL CRUSTACEA. 
28. Prof. F. M‘Coy, in 1849,” and again in 1854, thus classifies this group—“ Ord. 
Entomostraca, Trib. Pacilopoda. This group being distinguished from other Ento- 
mostraca by having crustaceous, didactyle, ambulatory, thoracic feet, as well as mem- 
branous, respiratory, abdominal ones, is, I think, clearly the place for those remarkable 
genera Hurypterus and Pterygotus.’ He adds further, “ The tribe Pacilopoda might be 
resolved into two families—Ist, Lemulide—Limulus; 2nd, Hurypteride—Lurypterus, 
Pterygotus, Bellinurus. 
29. Prof. M‘Coy* also figures and describes the head of Hurypterus cephalaspis, from 
Kendal (Pl. I 3, fig. 21), a somewhat doubtful form. His Pterygotus leptodactylus is 
founded on the tail-spines of Ceratiocaris, as pointed out by Mr. Salter. 
Like Dr. Hibbert,’ he attributes to Dr. Harlan (1835) the genus Lurypterus, which 
was established by Dr. J. E. Dekay * in 1825. 
30. Prof. F. J. Prormr®* (1854) places Hurypterus with the Copepoda, adopting 
Burmeister’s™ description. In the X¢phosura he places Limulus, Halycine, Bellinurus, 
and Pterygotus. 
31. In Prof. Ownn’s ‘ Lectures’ *’ (1855) we find the order Xiphosura placed in the 
sub-class Hntomostraca, along with the orders Zri/obita and Phyllopoda. 
32. Prof. A. E. Reuss,®” in 1855, gives a description of what he considers to be a 
new genus of Eurypterids, from the Coal Shale of Bohemia, preserved in the Prague 
Museum. He names it Lepidoderma Imhofi, but it is certainly a Hurypterus, judging, 
not only from his beautiful plates, but also from a cast sent to us by Dr. Anton Fritsch. 
Fie. 3. Pterygotus problematicus, Agassiz [copied from Prof. M‘Coy’s figure in Lyell’s ‘ Manual of Geology,’ 1855 (5th edition).] 
33. Prof. M‘Coy again, in 1855,® furnishes us with a classification and descriptions 
of species of this group; and in Sir Cuarzes Lyri’s Manual® he gives a restoration 
of Pterygotus problematicus, where he again expresses his belief in the close alliance 
of Pterygotus and Lurypterus, and of both these to the living King-crab, or Zimalus. 
34. In the same year Mr. Davin Pacn® named various species, and offered a 
restoration of Pterygotus. He observed that “The Péerygotus could be classed with no 
