No. 406.] DINOSAUR-AVIAN STEM. 793 
produced beyond the skin fold that encloses the bases of the 
quills. These proportions are peculiar to the nestlings ; the 
adults shorten the hand and lose the claws as soon as they have 
ceased to be of assistance ; but, as Pycraft observes, could we 
discover a yet more primitive form “it is probable we should 
find that the claws and long hand were maintained throughout 
life." Further light upon the quadrupedal habits of primitive 
birds is given by the very interesting observation of Dean upon 
the locomotion of young cormorants, which, when frightened, 
clamber over irregular surfaces with the assistance of the fore 
limbs. Young gallinules, coots, and grebes are also quadru- 
pedal in habit. 
So far, therefore, as the osteology of Archzopteryx and the 
embryology and habits of recent birds guide us, the theory of 
à quadrupedal proganosaurian prototype is not excluded. 
VI. Tue Most Primitive QuUADRUPEDAL LAND REPTILES. 
This suggests a consideration of the Proganosauria, the 
most primitive representatives of the Hatteria phylum, as one 
of the possible sources of the birds. 
The Proganosauria, Baur (= Proterosauria, Seeley), constitute - 
a suborder of Rhynchocephalia and include some of the most 
ancient reptiles known of the Permian period. They occupy 
the cleft between Crocodilia, Lacertilia, and Dinosauria. 
In his extremely interesting and important papers upon. 
Palzeohatteria and Kadaliosaurus Professor Hermann Credner 
(88,'89) has described two proganosaur types from the Per- 
mian, near Dresden, one of which approaches most nearly the 
hypothetical ancestral dinosaur. Palzeohatteria, if we may 
judge by the comparatively unossified extremities of the limb 
bones, was probably an aquatic type ; Kadaliosaurus, on the 
other hand, was undoubtedly a land type, the limb bones being 
completely ossified proximally and distally, with spongy inte- 
rior. The prefix xa6aX(cev refers to the exceptional elongation 
of the limbs, the proportions of which are well represented in 
Fig. 11. Professor Credner has pointed out the striking resem- 
blance of the somewhat forward and backward spreading ilium 
