1849.] EGERTON ON THE GANOIDEI HETEROCERCI. 5 



could not detect any specific character as diifering from P. speciosus. 

 It is possible some confusion may have arisen from the similar signi- 

 fication of the specific titles. 



Pal^oniscus Egertoni, Ag. Pl. I. fig. 2. 



This species, although named by Agassiz during his second visit to 

 England, has not yet been described. It was found by my brother 

 the Rev. W. H. Egerton in the coal shale at Silverdale in North 

 Staffordshire, and has since been discovered in Lancashire and York- 

 shire, as also, I believe, in some of the Scotch and Irish coal-fields. 

 It is a small and delicate species, somewhat less than PalcBoniscus 

 Robisoni. It is characterized by the scales, which are deeply fur- 

 rowed and serrated at the posterior margins *. The dorsal fin is large 

 and situated far back, its anterior insertion being very slightly in 

 advance of the anal fin. The fin rays are strong, and dichotomise 

 near their extremities ; the transverse articulations are distant. The 

 anal fin corresponds in size and character with the dorsal fin. The 

 pectoral fins are small and delicate. The ventral and caudal fins are 

 deficient. The head is smaller in proportion to the body than in any 

 other species. 



Pal^oniscus Monensis, Egerton. Pl. I. fig. 3. 



Lord Enniskilien found the specimens from which this species is 

 named in the shale brought out of a coal-pit in the Isle of Anglesea, 

 near the Holyhead road, a few miles from the Menai Bridge. They 

 are single scales which belonged to a larger fish than P. Egertoni, 

 and differ in external character from those of that species. The sur- 

 face is traversed by regular parallel grooves, the ridges between these 

 terminating in cusps at the posterior margin. In addition to these 

 a series of fine lines is distinctly seen, bordering two sides of the scale, 

 apparently indicating the annual increment. 



Since the completion of the 'Poissons Fossiles' the following species 

 have been made known: — 



Pal^oniscus Tchefkini, Fisch. 



This fish, from the Permian system of the Steppe of Kargala, is 

 figured by Fischer de Waldheim in the Bull. Nat. de Moscou. Sir 

 Roderick Murchisonf mentions three other species as probably be- 

 longing to this genus, found in the same Ste])pe near Orenburg. 



Pal^oniscus Gelberti, Goldf. Pl. I. fig. 4. 



Professor Goldfuss has given this name to a Palceoniscus discovered 

 by Herr Gelbert in the coal formation at HeimkirchenJ. He de- 

 scribes it as being longer and narrower than Palceoniscus Buvernoy, 

 and as differing from all other species of the genus in the ornament 

 of the scales. It is a handsome and well marked-species. 



* At p. 93, vol. ii. Poiss. Foss., Agassiz cancels the observation made at p. 41 

 as to the general smoothness of the scales of the Palceonisci fonnd in the coal- 

 measures, t ' Russia,' page 227, note. 



X Beitrage zur vorweltlichen Fauna des Steinkohleiigebirges, p. 17. 



