74 DENNIS, ON THE MICROSCOPIC 



laciinee, in fact, obey the same laws as tlie Haversian tubes 

 do, and are placed in that position, and arc of that form, 

 which best suits the necessities of the bones they constitute 

 a portion of. 



Since I had written the above remarks, I have very oppor- 

 tunely received a portion of a bone from the Chalk, throuoh 

 the kindness of H. Catt, Esq., of Brighton, which precisely 

 exhibits these characters. The Haversian tubes are princi- 

 pally longitudinal, the lacunae are long like those in the bill 

 of the pelican ; and, indeed, the Haversian tubes very nearly 

 compare, especially in size. There is, however, a pecidiarity 

 in the bone which I was not altogether prepared for, having 

 observed it in no bird-bones, though 1 have noticed some- 

 thing like it in the frog. It is the way in which the lacunae 

 cross.^ There appears to be a set running longitudinally, and 

 a set above them running in the opposite direction, which 

 gives a very marked and peculiar character to the bone, and 

 makes me think that this bone, which came from the Chalk, 

 and which is a hollow bone with very thin walls of a peculiar 

 texture, is pterodactyle bone ; another thing further confirms 

 me in this view, the canaliculi are not numerous like those 

 of birds, and coarser (it is figured in figs. 7 and 14) ; if so this 

 is a further confirmation of those general principles I laid 

 down in a previous paper on the characters of bone — the 

 pterodactyle, though it could fly like the bird or bat, yet 

 showing its saurian characters, both outwardly and inwardly, 

 in its bones. The fossil bone from Stonesfield, which I have 

 selected for comparison, is in the possession of W. Adams, 

 Esq., of Bmiton, Petersfield, who has very kindly fur- 

 nished me with other most interesting fossils ; and I have 

 chosen this from several other supposed fossil bones of 

 birds from Stonesfield, as one of the greatest interest, from 

 its striking similarity in structure to the humerus of the 

 heron. It belonged, however, to a smaller kind than our 

 common heron, and appears from a dra^ving, (for I have 

 only received fragments of the bone,) to be the distal end of 

 the humerus ; the bone has quite the texture of bird-bone 

 in its outward appearance, and is decidedly difi:erent from 

 that of the pterodactyle from the Chalk, w^hich looks rather 

 silky, an appearance apparently craised by fine lines on its 

 surface, Avhich the bird-bone is free from. 



The vertical section of a portion of this bone gives the 

 following characters : Haversian tubes for a bird of medium 



* I have since observed something lilce tiiis crossing in the skulls of sonic 

 birds and the bone jjlates of tlie arniadillo. 



