§ 45. BIRDS OF THE WEALDEN. 441 



nicated the result to the Geological Society. This eminent 

 microscopical observer has found a recognizable difference 

 in the form and proportion of the minute cells of the bones, 

 which he believes is constant, and by which the smallest 

 fragment may be referred to its proper class. In Birds, 

 under a power of 500 linear, by transmitted light, the 

 cells are found to have a breadth in proportion to their 

 length of from one to four or five ; while in Reptiles the 

 length exceeds the breadth ten or twelve times. For 

 example : — 



In the Albatross, the width of the cell is J the length. 

 — Crocodile — — — ^ — 



Applying this test to the supposed bones of birds from 

 the chalk, Mr. Bowerbank finds that the specimens re- 

 garded by Professor Owen as belonging to an extinct 

 species of Albatross,* are reptilian ; the length of the cells 

 being twelve times that of their width, as in the bones of 

 the cranium, jaws, &c. of an undoubted Pterodactyle 

 (P. giganteus) found in the same quarry, and to which he 

 therefore refers them, f 



The wealden bones, subjected to the same interrogatory, 

 gave different results. The bone figured Lign. 110 has 

 cells of the reptilian type, and is therefore declared by 

 Mr. Bowerbank to be that of a Pterodactyle : while some 

 of the other specimens (especially that examined by Baron 

 Cuvier, and figured in Geol. Trans, vol. v. PL XILLJlg. 6.) 

 have short elliptical cells as in true birds, and are presumed 

 to belong to that class. At the present time, the question 



* Medals of Creation, vol. ii. p. 803. 



t I would here remark, that these bones are so extremely thin, as to 

 render it most improbable that they could ever have sustained such 

 an instrument of flight, as the powerful wing of the Albatross or of 

 any other bird; their tenuity is in fact such as to point out their 

 adaptation to support an expanded membrane, but not pinions. 



