PTERYGOTUS GIGAS. 79 



Thoracic Appendages^ (?) (Mem. Geol. Surv., Mon. I, pi. xii, figs. 4 and 5). — The nature 

 of these is not understood, nor do these specimens show the characteristic irregular base. 

 But they differ specifically both from the similar appendages referred to P. problematic us 

 and P. arcuatus, by their deep terminal notch. The outer edges are thickened, and the 

 substance of the whole appendage is thick. The lateral plicae run down in oblique rows 

 on the inner (?) surface becoming more and more linear, till they become straight lines, 

 like the pennae of a feather, and on the outer side ; impressed distant converging striae 

 cut up, as it were, the whole surface into narrow bands, the termination of these bands 

 being serrated projections in P. problematicus, but in this species they come to an even 

 edge on the notched border. 



Ovisacs (?). — The egg-packets {Parka), found in plenty with this species at Trimpley, 

 show the membranous veil in several cases. The ova of considerable size, generally 

 oval, and placed a little apart in the younger packets, but they become hexagonal or 

 polygonal, from mutual pressure, in the older ones (see PL XVI, figs. 10 and 11). 



Localities. — Base of the Old Red Sandstone, at Ludlow Railway Station (abundant) ; 

 at Trimpley, north of Bewdley, associated with Pteraspis Banksii. 



Species 7.— PTERYGOTUS GIGAS —Salter. 1859. 



Pterygoids gigas, Salter. Mem. Geol. Surv., 1859, Mon. I, p. 83, pis. viii and ix. 

 — problematicus, Banks. Quart. Journ. Geol. Soc, vol. xii, 185G, p. 93, &c. 



Although there are very strong grounds for considering the remains referred to this 

 species to be only English representatives of the great Scotch Pterygotus anglicus, figured 

 in Part I of this Monograph, we have not treated it here as synonymous because we have 

 no new or more perfect materials to offer than those heretofore described in the ' Geolo- 

 gical Survey Monograph.' Therefore, in deference to Mr. Salter's determination, we 

 retain the species, giving his diagnosis, with only a few additional notes where needed. 



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 



1 I am at present quite unable to decide the true position of these fragments. (See Woodcut, Figs. 25 

 —27, p. 91.)— H. W. 



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