BRITISH FOSSILS. 



PLATES III. TO VII. 



PTERYGOTUS ANGLICUS. 



SPEC. CHAR. P. gigas, 6-8 ? pedalis, capite transverse, antice angus- 

 tiori truncato, segmentis corporis transversis, penultimo percarinato (subtus 

 carina brevi subcentrali), vix expanse, cauda ovata breviapiculata, carina 

 mediana paullo elevata. 



SYNONYMS. P. anglicus, AGASSIZ (1844), Poissons Foss. Vieux Gres 

 Rouge, pi. 1 ; M'CoY in LYELL (1855), Elem. Manual, 5th ed. pp. 419, 

 420 (restored). SALTER in MTJRCHISON'S Siluria, new edition (1859), 

 foss. 21, fig. 1, restored ; Trans. Brit. Assoc., 1856, Rep. Sections, p. 75. 

 Palteocarcinus alatus (AGASSIZ olim) fide PAGE, in Trans. Brit. Assoc., 

 1855, vol. xxiv. Rep. Sections, p. 90. 



The liberality of Lord Kinnaird and of the officers of the Watt 

 Institution, Dundee, has placed at our disposal a magnificent series 

 of this well-known species, including most of the fragments from 

 which Agassiz drew up his original description. We have also 

 to thank Colonel James, Director of the Ordnance Survey, and 

 Mr. David Page, of Edinburgh, for their kind co-operation. 



Until the carapace, Plate III. fig. 1, was obtained, no very com- 

 plete notion could be formed of the probable size of the fossil. It 

 was a less elongated species than P. acuminatus, but taking the 

 proportions of the head and the widest body rings as a guide, and 

 comparing these with such species as P. bilobus, the entire length 

 could not have been less than six, and from the size of the epistoma 

 and some other parts probably reached eight feet in length ! There- 

 are no living Crustacea which can match this in bulk. 



And it was apparently of considerable thickness, almost cylindrical ; 

 the crust, however, appears to be very thin and paper like, and only 

 thickened where requisite for the attachment of strong muscles, as 

 in the swimming feet ; or along the ridges and margins, the ser- 

 rated parts of the mouth, &c. 



The carapace, now first described from a young specimen, mea- 

 sures six inches and a half long and fully nine inches wide at the 

 broad base, but narrows considerably towards the front, where it is 

 less than five inches and a half broad. 



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