50 LECTURE III. 



Ordo VII. — LoPHOBRANCHii (Cuvicr). 



Endo-skeleton partially ossified ; exo-skeleton ganoid ; gills tufted, 

 opercular aperture small ; swim-bladder without air-duct. 



Fam. Hipiiocampidce, Example, Sea-horse. 

 Syngnathid(B, Pipe-fish. 



Ordo VIIL— Ganoidei.* 



Endo-skeleton in some osseous, in some cartilaginous, in some partly 

 osseous partly cartilaginous ; exo-skeleton ganoid ; fins usually with 

 the first ray a strong spine ; a swim-bladder and air-duct. 



Fam. Salamandroidei, Example, -! _, '^ "^ ' 



I Polypterus. 



PycnodontidcE, Pycnodus. 



Lepidoidei, Dapedius. 



a. • -J r Sturgeon. 



I Paddle-fish. 



Acanthodei, Acanthodes. 



DipteridfB, Dipterus. 



Cephalaspidce, Cephalaspis. 



Ordo IX. — Protopteri. 



Endo-skeleton partly osseous partly cartilaginous ; exo-skeleton as 

 cycloid scales ; pectorals and ventrals as flexible filaments ; gills 

 filamentary, free ; no pancreas ; swim-bladder as a double lung, with 

 an air-duct ; intestine with a spiral valve. 



Fam. Sirenoidei, Example, Lepidosiren. 



Ordo X. — HOLOCEPIIALI. 



Endo-skeleton cartilaginous ; exo-skeleton as placoid granules ; 

 most of the fins with a strong spine for the first ray, ventrals abdo- 

 minal ; gills laminated, attached by their margins ; a single external 

 gill aperture ; no swim-bladder ; intestine with spiral valve. Co- 

 pula gaudent. 



* I use this or<linal term of M. Agassiz in the sense in which it is restricted 

 by Professor J. Miiller. 



