Feb.,1895. THE STRUCTURE OF ARCHMOPTERYX. 113 



II. — The Skeleton of Arch^eopteryx. 



It will be noticed that the present article is not one of my 

 series upon Biological Theories, and it has nothing to do with my 

 contention in a previous article on the origin and multiplication of 

 errors. 



Apart from a single feather, only two specimens of A rchaopteryx 

 are known, and it is possible that these may not be identical in 

 species or even in genus. So far as we know them, the differences 

 between the two appear, to those who are best qualified to judge, 

 to be too small to justify separation into two species. Though both 

 were found in Bavaria, I shall refer to them as the " Berlin specimen " 

 and the " London specimen " respectively. 



It is not convenient to begin with a description of the 

 external form of the bird, as is customary with recent species, 

 for that external form can only be guessed at with reason- 

 able chance of guessing accurately after a careful consideration of 

 the structure of such parts as are still preserved. This is even more 

 conspicuously true of the habits of the animal. 



Of the skeleton, if we assume the two specimens to be so nearly 

 related that the characters exhibited in either may be taken as true 

 of both, we have quite an extensive knowledge. 



The vertebral column is readily divisible into four regions : 

 cervical, trunk, sacral, and caudal. Whether the vertebrae are fully 

 ossified or not it is difficult to say. I can find no justification for the 

 statement that they are amphicoelous. Professor Dames tell me that 

 his statement to that effect is a mere slip of the pen, and that he 

 intended only to say that, so far as can be seen in a specimen in 

 which the vertebra? are still in their natural relations with one 

 another, the ends are flat and not, as in most birds, saddle-shaped. 

 The central or internal part of each vertebra in the London specimen 

 is stated by Owen to be represented by a deposit of crystalline 

 " sparry matter " in the caudal region, while the outer " crust " 

 has adhered to the upper slab or " counterpart." Whether this 

 really shows that the vertebrae (of the tail) were mainly cartilage or 

 other soft tissue with only a crust of bone or not, may be open to 

 question. The perfectly-fitting joints, the large transverse processes 

 of the anterior caudal vertebra, and the slenderness and stiffness — 

 as shown by the straightness of the tail in both specimens — of this 

 region of the vertebral column are strong evidence that the bones 

 were well-ossified. 



Of the nine cervical vertebrae, only eight are well-preserved, 

 the first being almost unrecognisable. Measuring the lengths of the 

 centra of these on a large photograph (scale yf f ), I make the sum of 

 the eight in the Berlin specimen to be about 75 mm. ; but Professor 

 Dames gives numbers which together make only 6o'5. A glance at 

 the plate will show the position of the neck in this specimen. It is 



