ROOM III. WEALDEN PTERODACTTLES. 191 



fragments of bones of such tenuity as to indicate that they 

 belonged to animals capable of progression through the air, are 

 not uncommon. Their occurrence in the Wealden deposits 

 was first noticed in my earliest work, " On the Geology of 

 Sussex;" but, although thirty years have since elapsed, I 

 have not seen a specimen with articular extremities so perfect as 

 to demonstrate with certainty whether it belonged to a bird 

 or to a flying reptile. In the Case before us there are a few 

 portions of long bones which are probably metacarpals and 

 phalangeals of pterodactyles ; and in some of the closed 

 cabinets there are a few specimens more illustrative. There is 

 one bone, especially, which was formerly supposed to be the 

 tarso-metatarsal of a bird, but has since been ascertained to 

 be a humerus, and, probably, of a Pterodactyle ; although 

 there are certain points in which it unquestionably differs 

 from the arm-bone of any flying reptile hitherto observed. 



In the absence of obvious distinctive osteological cha- 

 racters, it was hoped that an investigation of the intimate 

 structure of these enigmatical remains would throw light on 

 the subject, and that the microscopical examination of the 

 most characteristic bones by Mr. Quekett and Mr. Bowerbank 

 might afford a solution of the problem. 



In a paper communicated to the Geological Society by Mr. 

 Bowerbank, that able observer affirms that there is a recog- 

 nisable difference in the form and proportion of the bone-cells 

 in birds and reptiles, which he believes to be constant, and by 

 which the smallest fragment of bone may with great pro- 

 bability be referred to its proper class. 



In birds, under a power of 500 linears, Mr. Bowerbank 

 found the cells to have a breadth in proportion to their 

 length, as 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 one-fourth the length, and 

 in the crocodile one-twelfth. 1 Applying this test to the 

 bones supposed by Professor Owen to be those of a bird allied 



1 Professor Owen remarks, " Such a statement as that these cells in 

 Birds have a breadth, in proportion to their length, of from one to four 

 or five, while in Reptiles the length exceeds the breadth by ten or twelve 

 times, only betrays the limited experience of the assertor /" and he 

 quotes " MantelTs Wonders of Geology," vol. i. p. 441. Now as the 

 statement in my work was submitted to Mr. Bowerbank's revision before 

 it was printed, the amiable Professor has missed his mark, and hit 



