22 NATURAL HISTORY OF BIRDS. 



bird. Till- sacral vcrtcbnc are fewer in mimhor than in any known bird, those 

 united tc)u'«'llH'r j>rob:iblj- K'ss tban five. 



Oni' of the most riiiiark:il)h' features of the Archaopterijx is the length of the tail, 

 which is as long as the rest of the body, consisting of twenty or twenty-one lung and 

 thin vertebne, exactly as in the reptiles, and widely differing from all other known 

 birds. It is in reference to this uni<iue structure of the tail that the snl)-class has been 

 named Saurura', or lizard-tailed birds. 



Professor Marsh has been able to determine the ]>resence of a single broad jilate, 

 constituting the sternum, which he thinks probably supported a keel, as the sca|)ular 

 arch, with its clistiiictly avian furculuin. strongly resembles that of modern birds. The 

 ril)s are very Hue, thin, curved, and ])i)inted at the end like surgeon's needles, and show 

 no flattening nor uncinate processes, according to Vogt ; but Dr. Ltltken thinks that 

 lie observed a trace of these processes, though admitting tliat the ribs are remarkably 

 thin, and unlike those of other birds. 



The arm ]»ro])er is truly avian. Only one carpal bone seems to be jiresent, but 

 with that exception the hand is just what may be seen in embryonic birds of to-<lay, 

 the three metacarpals being absolutely free, as in reptiles. When describing the first 

 sjiecimen. Professor Owen assigned four digits to it. 'J'he new one shows that this was 

 erroneous, as it has oidy three long, slender digits, armed with claws, hooked and 

 8liar|>-edged, on each hand; the radial digit, or the pollex, is the shortest; the other 

 two are nearly eijual, the second slightly the longer. The ]iii!lex is c<im])()se(l of 

 a short metacarpal, a pretty long phalanx, and of a terniinal claw-bearing ]ihalanx; 

 the other two digits have, besides the metacarpal, three normal phalanges. The jiollex 

 was free, like the other two digits. 



One of the most interesting results of Professor JIarsh's stmly of the London 

 specimen is the iletermination of the 8e])arate condition of the ])elvic bones, which, in 

 all other known adult birds, recent and extinct, are firmly anchylosed, while in the 

 young binls and in the Dinosainians they are distinct. 



The thigh and leg bones do not ]irescnt any peculiarity worthy of our attention in 

 the present connection, excejit that the distal end of the fibula stands in front of the 

 tibia, as in Ttjitanodon, but contrary to the condition in the birds. The feet do not 

 differ essentially from thos<' of living birds, though dee)i grooves between the three 

 elements of the metatarsus seem to indicate that the metatarsals of the second, third, 

 and fourth toes were distinct, or, .■Jt least, only imperfectly united. 



There remain the feathers, which, no doubt, air true bird's feathcr.s, with a median 

 shaft, having barbs ]ierfectly formed. 



The remiges of the winirs are fixed to the ulnar edge of the arm, and to the IimiicI; 

 tliey are covered for nearlv half their length with a fine filiform down. None ot them 

 project beyond the others; the wing is roinided in its outline like that of a fowl. It 

 is jtossible that at the base of the neck there was a ruff, like that of the condor. Some 

 traces of it are )ierhaps visible. The tibia was clothed with feathers for the whole of 

 its length. The .(/•'•A^o^(/pci/.c thus wore breeches, as do oiir falcons. Each caud:d 

 vertebra bore a pair of lateral rcctrices, an arrangement totally different from that of 

 all other known birds. 



All the rest ot the body — the head, neck, and trunk — were apparently naked and 

 unprovided with feathers, for no traces of either down or feathers are there to be 

 seen ; but it must be remembereil that the s]iccimen may h.avc lieen com])lotely decom- 

 posed before imliedded, and the small feathers or down carried away, while the larger 



