OF THE ORDER MEROSTOMATA. 33 
Order—MEROSTOMATA, Danza. 
Sub-Order—Evurypreripa, Hualey. 
Genus 1.—Prrryeotus, Agassiz, 1844. 
AutHoucn Luryplerus was the first-discovered genus of this sub-order, both in this 
country and also in America, as we have seen by the foregoing history, I have nevertheless 
preferred to commence this Monograph with the genus Péerygotus, as having become 
historically the most important in England; its affinities having been studied and its 
structure described by such distinguished naturalists and paleeontologists as Messrs. 
Agassiz, McCoy, Salter, Huxley, and Hall. 
The genus Pferygotus not only contains the largest species of the whole order, and 
probably of the whole Crustacean class, but the remains of several of the species are 
exceedingly perfect and complete. Even the great Pterygotus anglicus, which forms the 
subject of this chapter, once only known by a few gigantic fragments, is now capable of 
restoration from almost entire specimens figured in the accompanying plates. 
For the discovery and preservation of these very perfect remains we are indebted to 
the accurate geological knowledge and untiring exertions of Mr. James Powrie, I’.G.S., of 
Reswallie, Forfar, who durmg many years has not only encouraged the quarrymen to 
preserve the organic remains from the ‘‘ Arbroath paving-stone ” and overlying shales, but 
has also personally worked in the quarries of the district for days and weeks together to 
procure specimens. 
No higher testimony can be afforded as to the value of my friend’s labours than by 
referring to the accompanying plates, the materials for which were nearly all furnished by 
his own museum, those figured from the British Museum having likewise been procured 
and presented by him. 
The great “ Seraphim” of the Scotch quarrymen, Pterygotus anglicus of Agassiz,’ was 
the first species described* (1844), and is now very well represented, not only in detail, 
by numerous detached organs and parts of bodies, but also by four nearly entire bodies of 
various sizes. 
1 See Bibliography, p. 22, J 20. 
2 In Murchison’s ‘ Silurian System’ (1839), p. 606, pl. iv, figs. 4 and 5, two fragments of Péerygotus 
are figured and described by Prof. Agassiz under the name of Sphagodus pristodontus ; these have since been 
referred by Mr. Salter (Mem. Geol. Survey, Mon. I, p. 89) to P. problematicus, Ag. 
