PAL^ONISCUS, GYROLEPIS, AND PYGOPTERUS. 577 



the name must consequently drop. The only statement made re- 

 garding it by Agassiz, is as follows : — 



" Pygopterus Jamesoni, Agass. Sous ce nom j'ai distingue une 

 seconde espece de Burdiehouse, dont je ne connais encore que la 

 machoire inferieure qui differe de celle du P. mandibulars, en ce 

 qu'elle est proportionnellement plus courte "*. As he does not, how- 

 ever, state how this jaw (the only relic found) differs from that of 

 P. (ElonicJithys) Bucklandi, I cannot help strongly suspecting that 

 it belonged to the same fish. 



The scale figured by Mr. T. P. Barkas f , from the Northumberland 

 coal-field, as belonging to a species of " Pygopterus " evidently 

 appertains to the same fish as that from North Staffordshire, 

 described by myself as ElonicJithys semistriatus, as is also most pro- 

 bably the case with the mandible represented by him on the same 

 plate £. 



III. Type of Pygopterus GreenocMi, Agass. (genus Nematoptychivs, 

 Traquair). — Concerning " Pygopterus " GreenocMi the following 

 brief statement was made by Agassiz : — 



" Espece tres-distincte sous le rapport specifique, mais douteusc 

 sous le rapport generique. Les fragmens connus ne sont guere que 

 des tetes avec la partie anterieure du tronc. Les ecailles qui re- 

 couvrent cette partie du corps sont plus hautes que longues, et 

 different par-la de celles de tous les autres Pygopterus. Du terrain 

 houiller de Newhaven. II en existe plusieurs exemplaires dans la 

 collection de Lord Greenock, qui sont tous contenus dans des geodes 

 de fer hydrate carbonate " §. 



Although the original examples of this species, collected by Lord 

 Greenock, and now in the Museum of the Royal Society of Edin- 

 burgh, were thus imperfect, there is hardly any Carboniferous fish 

 concerning whose structure I have been able to acquire more com- 

 plete information, my own collection being especially rich in its 

 remains, and many other specimens being in the Edinburgh Museum 

 of Science and Art. These specimens, some of them entire, con- 

 firm the doubts which Agassiz himself entertained regarding its 

 generic position ; and accordingly in 1875 || I proposed for its recep- 

 tion the new genus Neinatoptychius. The configuration of the scales 

 is alone sufficient to demand its separation from Pygopterus. Those of 

 the flanks are much higher than broad ; their anterior covered 

 margin is very narrow ; the exposed surface is rhomboidal ; but the 

 acute angles are the anterior-inferior and posterior-superior ; the 

 articular spine is broad and triangular, and arises from the whole, 

 or nearly the whole, of the narrow upper margin. The scales alter 

 their form on the ventral aspect, where they become low and very 

 small ; their external ornament consists of fine, wavy, thread-like 

 ridges. The pectorals are of moderate size, and have their principal 



* ' Poissons Fossiles,' vol. ii. pt. 2, p. 78. 



t ' Manual of Coal-measure Palaeontology,' pi. 4. fig. 130. 



\ Ibid. fig. 131. 



§ ' Poissons Fossiles,' vol. ii. pt. 2. p. 78. 



I! Ann. & Mag. Nat. Hist. (4) vol. xv. pp. 258-262. 



