1907.] 



ORIGIX OF FLIGHT. 



233 



and as a sign of cursoiial locomotion there is even an indication 

 of a processus pectinealis. The vertebrae are free, and neiu^al 

 spines are present. 



Besides this, Arcliceopterycc differs from all Birds by having a 

 long laterally feathered tail, that to a certain degree reminds us 

 of the peculiarly covered and flat-looking tails in the mammals 

 Acr abates and Ptilocerus lotvi. 



Text-fio-. 81. 



Hind limb of Areh(Bnj)teri/x. 

 (Photograph of the British Museum type specimen.) 



The ossified tendons which occur in the tail of Archmopteryx 

 show further that strength of this organ was required just 

 as much as in the tail of Dimorpliodon or Rhmnphorhynchus. 

 A long tail, sometimes even with ossified tendons, is quite a marked 

 feature of the Dinosaurian bipedal reptiles, and its loss, as shown 

 in Pterosaurs, is generally in harmony with the better adaptation to 

 flying locomotion. 



The rounded contour of the Archceopteryx-\\m.g, together with 

 the feebly developed sternum, show us that Archceopteryx, though 

 perhaps not an altogether badly flying creature, can on no account 

 have been a soaring bird, but a bird that was yet in the first 

 stage of active flight. 



That the soaring Frigate- Birds and Albatrosses have a com- 

 paratively weaker sternum than the Gallinaceous Birds has already 

 been mentioned ; and 1 therefore need only point to the formation 

 of a ligid thorax in flying birds as analogous to the condition in 

 Pterosaurians and Bats and in opposition to the Ratitte, and to 

 the fact that the cursorial Palseognathee, contrary to the flying 



Peoc. Zool. Soc— 1907, No. XVI. 16 



