BRITISH FOSSILS. 



PLATES VIII AND IX. 



PTEEYGOTUS GIGAS. 



SPEC. CHAR. P. maximus, 6-7 pedalis (?), capite haud truncate, semiovato ; 

 oculis anticis rotundis ; segmentis corporis ut in P. anglico, penultimo 

 expanse emarginato, insuper piano, subtus carina mediana postica : cauda 

 rnagna ovali, crista elevata centrali (apice emarginato ?). 



SYNONYM. P. problematicus, BANKS, Quart. Journ. Geol. Soc., vol. 

 xii. pp. 93, &c. 



For some years a large Pterygotus has been known in the beds of 

 Downton Sandstone (Uppermost Ludlow Rock), worked for building 

 purposes at Kington, Herefordshire, and a description of many of its 

 parts was given by Mr. R. Banks, of Ridgbourne, in the Quarterly 

 Journal of the Geological Society for 1856. Since his description 

 was written, he has continued to labour assiduously to collect the 

 fragments, and has been fortunate enough to discover nearly all the 

 parts of this fine species. He has generously placed these fragile 

 specimens in our hands, and presented a series of excellent drawings, 

 which were formerly exhibited at the Geological Society.* In the 

 paper quoted above, the fragments were all considered to belong 

 to the P. problematicus of Agassiz, a species for which there is un- 

 fortunately very scanty material, but which, as originally described 

 (see below, Plate XII.) is a Ludlow Rock species identical with one 

 of the Kington fossils, but not apparently with the principal and 

 largest of them, here described, and which in many respects is very 

 like P. anglicus. 



P. gigas has, in common with the latter species, the open scale- 

 like sculpture on the body rings, and the thick tubercular scales on 

 their margin ; the shape of the epistome and head is very similar, 

 but the latter is rounded and not truncate in front. The penulti- 

 mate body ring is wider and has a short keel on the upper surface 

 only (while P. anglicus has one on both sides above and below), ana 



* See Quart. Journ. as above, note to p. 97. It ought to have been named after him, 

 had not a much smaller Kington species been already distinguished by his name. 



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