STRUCTURE AND HABITS OF ARCH^EOPTERYX. 269 



It measures 26 mm. in length. It is probable that there are about 

 seven sacral vertebree. 



The vertebrae of the tail, twenty in number, measure together about 

 170 mm. — slightly less perhaps. The first few are very short and 

 stout, each measuring about 4 mm. in length and 4 mm. in height. 

 The first four have well developed transverse processes ; in the fifth 

 this process is not well preserved, and the vertebra? behind this 

 have no transverse processes, but only a ridge. The vertebrae are 

 longest nearer the middle of the tail, the eleventh measuring nearly 

 12 mm. The tail as a whole seems to have had little flexibility, for 

 it is almost perfectly straight in both specimens. The tale of the 

 London specimen has apparently only eighteen vertebrae and measures 

 180 mm. 



The skull has been much further exposed since the photograph was 

 taken. It is large and fairly massive, the jaws are stout, and teeth 

 are very easily made out in the upper jaw. Those of the lower jaw 

 are, however, hidden by those of the upper, and it is impossible to say 

 at present how many there were. The sclerotics are ossified. The 

 hinder part of the skull is destroyed in the Berlin specimen, and it is 

 worthy of note that the cranial cavity was not filled with matrix. 

 No part of the skull is recognisable with certainty in the London 

 specimen, though it may be that the supposed cast of the brain (!) 

 is a portion of the skull. 



The ribs, both vertebral and ventral, are very slender. There are 

 no uncinate processes visible. 



Of the sternum nothing is known, though much has been written. 

 In the Berlin specimen it probably lies still hidden in the matrix. 

 The position of the ventral ribs shows that it must have been small. 



The scapulcH in the Berlin specimen were broken in exposing the 

 specimen. The right one is easily recognisable in Plate XV. They 

 are flat curved bones, not unlike those of a modern bird. Their length 

 is 43 mm. or thereabouts, according to Dames. In the photograph 

 only a portion is seen. 



The coracoids are in the Berlin specimen largely hidden. I have 

 not specially examined what portion is exposed in the London specimen. 

 The dorsal ends are exposed in the Berlin specimen and possess a 

 furcular tuberosity as in other birds. 



