6o8 The Crossopterygii 



The Polypteridse. — All the Polypterida; are natives of Africa. 

 Two genera are known, no species having been found fossil. 

 Of Polypterns, Boulenger, the latest authority, recognizes nine 

 species: six m the Congo, Polypterns congiciis, P. delhezi, P. 

 ornatipinnis, P. weeksi, P. palnias, and P. retropinnis; one, P. 

 lapradei, in the Niger ; and two in the Nile, Polypterns bichir and 

 P. endlicheri. Of these the only one known until very recently 

 was Polypterns bichir of the Nile. 



These fishes in many respects resemble the garpike in 

 habits. They live close on the mud in the bottom of sluggish 

 waters, moving the pectorals fan-fashion. If the water is 

 foul, they rise to the siirface to gulp air, a part of which escapes 

 through the gill-openings, after which they descend like a flash. 

 In the breeding season these fishes are very active, depositing 

 their eggs in districts flooded in the spring. The eggs are very 

 numerous, grass-green, and of the size of eggs of millet. The 

 flesh is excellent as food. 



The genus Erpetoichthys contains a single species, Erpetoich- 

 iJiys calabaricns* found also in the Senegal and Congo. This 



Fig. 380. — Erpetoichthys calaharicus Smith. Senegambia. (After Dean.) 



Species is very slender, almost eel-like, extremely agile, and, as 



usual in wriggling or undulating fishes, it has lost its ventral 



fin. It lives in shallow waters among interlaced roots of palms. 



When disturbed it swims like a snake. 



* This genus was first called Erpetoichthys, but the name was aftenvards 

 changed by its author, J. A. Smith, to Calamoiclithys, because there is an 

 earlier genus Erpiclilhys among blcnnies, and a H erpetoichthys among eels. 

 But these two names, both wrongly spelled for Herpetichthys, are sufficiently 

 different, and the earlier name should be retained. "A name in science is a 

 name without necessary meaning" and without necessarily correct spelling. 

 Furthermore, if names are spelled differently, they are different, whatever 

 their meaning. The efforts of ornithologists, notably those of Dr. Coues, 

 to spell correctly improperly formed generic names have shown that to do 

 so consistently would throw nomenclature into utter confusion. It is well 

 that generic names of classic origin should be correctly formed. It is vastlv 

 more important that they should be stable. Stability is the sole function 

 of the law of priority. 



