196 Dr. H. Woodward — On Eurypterus Scouleri, Hibbert. 



Blackdown form bearing the same name, but is identical with a 

 large variety of that species which has occurred rarely in the Whet- 

 stones of Little Haldon, figured as T. dcedalea, var. confusa, in the 

 Monograph above quoted, pi. 23, fig. 1. Fine examples of the 

 latter form are exhibited upon the tablets of the British Museum as 

 T. dcedalea, Park. Other Trigonice occur in the Belgian beds, but 

 the two here alluded to are the most abundant and characteristic 

 species. 



III. — Notes on Paleozoic Crustacea. 



Eurypterus Scouleri, Hibbert. 



By Henry "Woodward, LL.D., F.E.S., etc. 



(PLATE V.) 



AMONG- the many relics of Palaeozoic life-forms which the 

 Carboniferous formation has yielded to the palaeontologist, 

 none is more remarkable than " Scouler's Eidothea," or the Eury- 

 pterus Scouleri of Hibbert. 



This fossil Crustacean is of itself sufficiently bizarre in aspect to 

 arrest the notice of even the most casual observer, whilst its geo- 

 logical history is equally curious. 



The Carboniferous epoch, however, is rich in interest ; for it is, 

 above all others, that, at which the ideal boundary-line for the 

 Biologist should be drawn, which marks more clearly than any 

 other the incoming of the recent, and the outgoing of the extinct 

 faunas of our globe. 



As we scan the record of these old Carboniferous rocks, so rich in 

 organic remains, we seem to stand on some lofty beacon-hill, whence 

 we can casb our glance upwards and downwards along the stream 

 of Time. 



Beneath our feet lie buried the last representatives of those 

 aboriginal races, now quite extinct, the Trilobita and the Eurypterida, 

 whose ancient hosts peopled the seas of the Devonian and Silurian 

 ages, and reached far away into the Cambrian epoch. Beside them 

 lie the earliest representatives known of our modern Decapoda, 

 Stomapoda, and Isopoda, then but few and feeble, but now the 

 dominant races of the Crustacean class. 



Eurypterus Scouleri is the last representative of the extinct Eury- 

 pterida — probably the only order in the class Crustacea which have 

 really died out. For the modification necessary to convert the 

 extinct order Trilobita into its modern representative order, the 

 Isopoda, seems a far lesser metamorphosis of organs than that needed 

 to transform the aquatic branchiated order Eurypterida into the 

 terrestrial pulmonated Arachnida (Scorpionidae) ; yet not only these, 

 but many other similar modifications, resulting in the extinction of 

 the older type and the extension of the newer form, have doubtless 

 taken place since the Carboniferous epoch. 



This last species of Eurypterus, of which our plate affords an at- 

 tempted restoration, has been fully described, so far as the materials 

 existing admitted, in a Monograph on the Merostomata, by the writer. 

 (See Pal. Soc. Mons. 1866-78. Part IV. 1872, pp. 133-139.) 



