﻿470 ACTINOPTEEYGIT. 



Genus PYGOPTERUS, Agassiz. 

 [Poiss. Foss. vol. ii. pt. i. 1833, p. 10, and ibid pt. ii. 1844, p. 74.] 



Trunk elongated, gradually tapering from the occiput. Mandi- 

 bular suspensorium oblique ; dentition consisting of a series of large 

 well-spaced conical teeth, and more numerous small teeth forming 

 an outer series ; opercular apparatus relatively small ; all the head 

 and opercular bones ornamented with striations. Fins well deve- 

 loped, with fulcra, the rays flattened and unornamented, mostly 

 articulated and branched. Pectoral fins having the principal rays 

 unarticulated, except distally ; pelvic fins relatively small and short- 

 based ; dorsal fin opposed to, or arising slightly in advance of the 

 anal, high and acuminate in front, with a scarcely elongated base- 

 line ; anal fin much extended, high and acuminate in front, but low 

 and fringe-like in its hinder half ; upper caudal lobe much elongated, 

 the fin deeply forked and nearly equilobate. Scales relatively small, 

 thin, smooth or feebly ridged, those of the flanks of the abdominal 

 region scarcely deeper than broad, and those of the ventral aspect 

 not much broader than deep, except in the caudal region : the peg- 

 and-socket articulation of the principal scales large and prominent. 



Pygopterus humboldti, Agassiz. 



1709. Figure by G. F. Mylius, Memorabilia Saxonise subterr. pt. i. fig. 1. 

 1719. Figures by P. Wolfart, Hist. nat. HassiaB inf. pt. i. pis. xviii., xix. 

 1818. Palceothrissum magnum, H. D. de Blainville, Nouv. Diet. d'Hist. 



Nat. vol. xxvii. p. 321. 

 1818. Esox eislebensis, H. D. de Blainville, ibid. p. 322. 

 1829. "Fossil fish," A. Sedgwick, Trans. Geol. Soc. [21 vol. iii. 



p. 118, pi. x. 

 1833. Pygopterus humboldti, L. Agassiz, Poiss. Foss. vol. ii. pt. i. p. 10. 

 1833. Pygopterus scoticus, L. Agassiz, ibid. p. 10 (includes undefined 



species Nemopteryx mandibulars and Sauropsis scoticus). 

 1835. Pygopterus humboldti, F. A. Quenstedt, Wiegmann's Arckiv, 



Naturg. vol. ii. p. 93. 

 1835. Pygopterus scoticus, F. A. Quenstedt, ibid. p. 93. 



1839. Pygopterus humboldti, G. A. Kurtze, Comment. Petrefact. Mans- 

 feld. p. 25. 



1840. Pygopterus humboldti, E. F. Germar, Verstein. Mansfeld. Kupfer- 

 schief. p. 22. 



1842. Pygopterus humboldti, G. von Miinster, Beitr. Petrefakt, pt. v. 



p. 48, pi. v. fig. 1. 

 1844. Pygopterus humboldti, L. Agassiz, Poiss. Foss. vol. ii. pt. ii. p. 74, 



pis. liv., lv. 

 1844. Pygopterus mandibulars, L. Agassiz, ibid. p. 76, pis. liii., liii. a. 



