GANOID FISHES. 425 
Selachians, Ganoids, and Batrachians. Chimera plumbea 
3ill lives in deep water off the coast of New England. 
Subclass 2. Ganoidei (Garpikes, Mud Fishes).—The 
erm Ganoid was applied to these fishes from the form of 
the scales, which in most of the species are angular, square, 
ox rhomboidal and covered with enamel, as seen in the com- 
non garpike. In others, however, as in the Amia and Dip- 
1oans, the scales are rounded or cycloid. These fish, 7.¢., 
neluding Pterichthys and Cephalaspis, were the character- 
stic fishes of the Devonian age, which has consequently been 
‘alled the Age of Fishes, there being no bony fishes (Tedeos- 
ei) at that time. The forms were much larger than at 
owresent, far more numerous in species, genera, and families, 
ind they, with the sharks, were the rulers of the sea. 
At the present day the type is nearly extinct, being repre- 
ented by such isolated forms as the sturgeon, the paddle-~ 
ish, the Scaphirhynchops, the garpikes, and the American 
nud-fish (Amia). Like most of the paleozoic types of life, 
he Ganoids were both generalized forms and also combined 
he characters of classes of animals not then in existence ; in. 
ther words they were synthetic or comprehensive types. 
Chus in forms like Amia, the Teleostean fishes were antici-~ 
vated ; in the Dipnot, with their external gills and lungs,, 
iot only the Amphibians, but even the reptiles were indica« 
ed in their hearts with two auricles, just asthe Trilobites and! 
Verostomata, as indicated by the structure of the living: 
cing-crab, combined with the structure of Crustaceans, fea- 
ures which became in a degree reproduced in the terrestrial 
corpions and spiders which subsequently appeared. Owing 
o this intermixture of ancient and modern characteristics, 
his reaching up and out of the piscine type of life over into: 
he amphibian and reptilian boundaries, the classification, 
.¢., actual position in nature of the Ganoids, becomes very 
lifficult, and the views of naturalists regarding their system- 
tic position are very discordant. If, as insisted on by Gill, 
ve recognize the fact that the Ganoids are an older, more 
eneralized, and therefore more elementary group, and the 
igseous fishes a newer, more highly specialized group, and 
