Subclass Dipneusti, or Lung-fishes 245 
peat. Their galleries run horizontally and are usually two feet 
long by eight inches wide. After the eggs are laid the male 
remains curled up in the nest with them. In the spawning 
season an elaborate brush is developed in connection with the 
ventral fins. 
Protopterus, a second genus, isfound in the rivers of Africa, 
with three species, P. annectens, P. dollot, and P. ethiopicus. 
The genus has five gill-clefts, instead of four as in Lepidosiren. 
It retains its external gills rather longer than the latter, and 
its limbs are better developed. The habits of Protopterus are 
essentially like those of Lepidosiren, and the two types have 
developed along parallel lines doubtless from a common ancestry. 
No fossil Lepidosirenide are known. 
Fig. 182.—Protopterus dollot Boulenger. Congo River. Family Lepidosirenide. 
Arthrodires.— The large group of Arthrodires consists of 
mailed and helmeted fishes with distinct jaws and other charac- 
ters separating them widely from the Ostracophores. In the 
latest view, that of Woodward and Eastman, these fishes con- 
Fie. 183.—An Arthrodire, Dinichthys intermedius Newberry, restored. Devonian. 
stitute an order of Dipnoans. As they are all extinct, the 
reader is referred to the ‘‘Guide to the Study of Fishes” for 
further discussion. 
Cyclie.—The hypothetical suborder, Cycliz, based on the 
extinct genus Palgospondylus, may be similarly treated. 
