234 PERMIAN FOSSILS. 



dorsal fin. This remarkable discrepancy in form and proportion is associated 

 with other peculiarities in the outline, number, and character of the scales. 

 As in other species of the genus, these are small and uniform, but they are more 

 numerous, there being not less than sixty in each dorso-ventral series in the broad 

 part of the body. The arrangement of each series is less oblique ; and the scales are 

 less elongated, especially near the tail, than in Pygopterus mandihularis. The scales are 

 ornamented with four or five distinct ridges, somewhat in the manner of those of 

 Acrolepis. These are not so numerous^ nor so prominent in the caudal region. The 

 bones supporting the dorsal fin rays are strong and much compressed : those of the 

 anal fin are larger and more numerous, but not flattened. It is a very distinct and 

 well characterised species. — P. G. E. 



Sir Philip Egerton's specimen of this species was found in the Marl-Slate of 

 Ferry-Hill. 



Genus Acrolepis, Agassiz. 



AcROLEPis Sedgwickii, Agassiz. Plate XXV, fig. 1 a, b, c. 



Fragment of a fossil fish ; species not ascertained, Sedgiviek. Trans. Geol. Soc. 



Lond., 2(1 series, vol. iii, p. 117, pi. viii, figs. 3, 4, 1829. 

 Acrolepis Sedgwickii, Agassiz. Poiss. Foss., vol. ii, part ii, pp. 80, 81, pi. Iii. 



— — ,, Bronn, Lethsea Geognostica, vol. ii, p. 128, pi. x, 



fig. 6, 183.5. 

 Ann. Mag. Nat. Hist, vol. vii, p. 488, 1841. 

 Morris, Catalogue, p. 187, 1843. 

 Rep. 13tli Meet. Brit. Assoc, p. 198, 1844. 

 De Verneviil, Bull. Soc. Geol. de France, 2"'" serie, 



vol. i, p. 40, 1844. 

 Geol. Russ., vol. i, p. 227, 1845. 

 Tennant, Strat. List, p. 89, 1847. 

 King, Catalogue, p. 15, 1848. 

 Howse, Trans. T. N. F. C, vol. i, p. 236, 1848. 



The specimen selected to give the best idea of this interesting species is from my 

 own collection. Although it is rather more perfect than Mr. Witham's specimen 

 figured in the ' Poissons Fossiles ;' yet it is deficient in those parts still wanting to 

 complete the description of the species, viz. the head, and scapular arch and appen- 

 dages. The account given by Agassiz is so full and accurate, that it is unnecessary to 

 repeat it here, especially as the subject of the plate was examined by Agassiz before 

 his detailed description was printed. Since the publication of the ' Poissons Fossiles,' 

 a species of this genus has been discovered in the Coal-shale of Berschweiler near 

 Kirn, on the Nahe, so that every genus of Permian fish is now known to be common 

 to that system and the Coal-measures. — P. G. E. 



Acrolepis Sedgwickii occurs in Marl-slate at East Thickley, Ferry-Hill, Thrislington 

 Gap, and Whitley. 



