234 The Crossopterygii 
The Polypteride.—All the Polypteride are natives of Africa. 
Two genera are known, no species having been found fossil. 
Of Polypterus, Boulenger, the latest authority, recognizes nine 
species: six in the Congo, Polypterus congicus, P. delhezi, P. 
ornatipinnis, P. weeksi, P. palmas, and P. retropinnis; one, P. 
lapradei, in the Niger; and two in the Nile, Polypterus bichir and 
P. endlicheri. Of these the only one known until very recently 
was Polypterus 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 surface 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, Erpeto:ch- 
thys calabaricus,* found also in the Senegal and Congo. This 
Fia. 169.—Erpetoichthys calabaricus 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 Erpetoichihys, but the name was afterwards 
changed by its author, J. A. Smith, to Calamoichthys, because there is an 
earlier genus Erpichihys among blennies, and a Herpetoichthys 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 vastly 
more important that they should be stable. Stability is the sole function 
of the law of priority. 
