22 NATURAL HISTORY OF BIRDS. 



bird. The sacral vertebrae are fewer in number than in any known bird, those 

 united together probably less than five. 



One of the most remarkable features of the Archceopteryx is the length of the tail, 

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

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

 birds. It is in reference to this unique structure of the tail that the sub-class has been 

 named Saururae, or lizard-tailed birds. 



Professor Marsh has been able to determine the presence of a single broad plate, 

 constituting the sternum, which he thinks probably supported a keel, as the scapular 

 arch, with its distinctly avian furculum, strongly resembles that of modern birds. The 

 ribs are very fine, thin, curved, and pointed at the end like surgeon's needles, and show 

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

 he observed a trace of these processes, though admitting that the ribs are remarkably 

 thin, and unlike those of other birds. 



The arm proper is truly avian. Only one carpal bone seems to be present, but 

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

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

 specimen, Professor Owen assigned four digits to it. The new one shows that this was 

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

 sharp-edged, on each hand ; the radial digit, or the pollex, is the shortest ; the other 

 two are nearly equal, the second slightly the longer. The pollex is composed of 

 a short metacarpal, a pretty long phalanx, and of a terminal claw-bearing phalanx ; 

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

 was free, like the other two digits. 



One of the most interesting results of Professor Marsh's study of the London 

 specimen is the determination of the separate condition of the pelvic bones, which, in 

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

 young birds and in the Dinosaurians they are distinct. 



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

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

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

 differ essentially from those of living birds, though deep grooves between the three 

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

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



There remain the feathers, which, no doubt, are true bird's feathers, with a median 

 shaft, having barbs perfectly formed. 



The remiges of the win^s are fixed to the ulnar edge of the arm, and to the hand; 

 they are covered for nearly half their length with a fine filiform down. None of them 

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

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

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

 its length. The Archoeopteryx thus wore breeches, as do our falcons. Each caudal 

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

 all other known birds. 



All the rest of 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 remembered that the specimen may have been completely decom- 

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



