GANOIDEI. 355 



SECOND SUB-OEDER— ACANTHODINI. 

 Extinct. Body oUong, compressed, covered with shagreen ; 

 skull not ossified ; caudal heterocercal. Large spines, similar 

 to those of Chondropterygians, in front of some of the median 

 and paired fins. The spines are imbedded between the muscles, 

 and not provided with a proximal joint. 



Acanthodes, Ghiracanthus, from Devonian and Carbonifer- 

 ous formations. 



THIED SUB-OEDER— DIPNOI. 



Nostrils two pairs, more or less within the mouth ; limbs 

 with an axial skeleton. Lungs and gills. Skeleton noto~ 

 chordal. No hrancMostegals} 



First Family — Sieenid^.. 



Caudal fim, diphycercal ; no gular plates ; scales cycloid. A 

 pair of inolars, above and below, and one pair of vomerine teeth. 



Lepidosikbn. — Body eel-shaped, with, one continuous vertical 

 fin. Limbs reduced to cylindrical filaments, without fringe. 

 Vomerine teeth conical, pointed. Each dental lamina or molar 

 with strong cusps, supported by vertical ridges. No external 

 branchial appendages ; five branchial arches, with four interven- 

 ing clefts. Conus arteriosus with two longitudinal valves. 

 Ovaries closed sacs. 



One species only is known from the system of the Eiver 

 Amazons (Z. paradoxa). It must be very locally distributed, 

 as but a few specimens have been brought to Europe, and all 

 recent endeavours to obtain others have been unsuccessful. 

 Natterer, by whom this most interesting iish was discovered, 

 states that he obtained two specimens, one on the Madeira 

 Eiver, near Borba ; the other in a backwater of the Amazons, 

 above Villa Nova. The natives of the former place called it 

 Caramurii, and considered it very scarce. The larger indivi- 



1 See pp. 73 and 74, Figs. 35 and 36. 



