The Crossoptery gii 231 
single family Celacanthide. In Celacanthus the fin-rays are 
without denticles. Celacanthus granulatus is found in the 
European Permian. Celacanthus elegans of the coal-measures 
is found in America also. In Undina the anterior fin-rays are 
marked with tubercles. Undina penicillata and Undina gulo 
from the Triassic are well-preserved species. In M acropoma 
(lewesiensis) the fin-rays are robust, long, and little articulated. 
ee 
Vy) } KYW ‘ 
Fie. 165.— Undina gulo Egerton; Lias. Family Celacanthide. (After Woodward.) 
Other genera are Heptanema, Coccoderma, Libys, Diplurus, 
and Graphiurus. Diplurus longicaudatus was found by New- 
berry in the Triassic of New Jersey and Connecticut. 
Order Cladistia.—In the Cladistia the axis of the pectoral 
limb is fan-shaped, made of two diversified bones joined by 
cartilage. The notochord is restricted and replaced by ossi- 
fied vertebre. The axonosts of the dorsal and anal are in 
regular series, each bearing a fin-ray. The order contains the 
single family Polypteride. In this group the pectoral fin is 
formed differently from that of the other Crossopterygians, 
being broad, its base of two diverging bones with cartilage 
between. This structure, more specialized than in any other 
of the Crossopterygians or Dipneusti, has been regarded by 
Gill and others, as above stated, as the origin of the fingered 
hand (chiropterygium) of the frogs and higher vertebrates. 
The base of the diverging bones has been identified as the ante- 
cedent of the humerus, the bones themselves as radius and 
ulna, while the intervening non-ossified cartilage breaks up 
into carpal bones, from which metacarpals and digits ulti- 
mately diverge. This hypothesis is open to considerable doubt. 
