MACKIE — ON FOSSIL BIRDS. 
21 
birds. It seems therefore possible, from tbe microscopic structure of the 
bone of a bird, to divine the shape of its wing and the character of its flight, 
there being a perfect correspondence one with the other, just as a perfect 
knowledge of the femur will inform us whether a bird could swim, or only 
ran or walked." 
And this, he thinks, may be done even from a fragment of a bone, 
" after we have acquainted ourselves with the general principles by 
very numerous and exact observations." 
" In the coracoid, for instance, the ordinary disposition of the Haversian 
tubes would be lougitudinal, braced more or less, because that woidd be 
the best arrangement to resist the powerful action of the pectoral muscles. 
. . . The ulna of the razor-bird and guillemot is more reticulated than 
would primarily be expected in the wing of a bird when the secondary 
quills are so very weak ; but then it must be considered that those birds 
use their wings much more like fins when under water than as instruments 
of flight," etc. 
Having so far grappled with the general features of the micro- 
scopic characters of birds, Mr. Dennis takes up the microscopic 
structure of rterodactyles. It must not, however, be forgotten that 
we are quoting an author who Avas amongst the first to investigate 
the subject, and whose painstaking and details are therefore the more 
worthy of credit to himself, and useful to the student, from their 
elaborate minuteness. 
" The Fterodactylus longirostris perhaps affords us the most perfect 
means of studying the singular proportioiiS of its skeleton. A larger and 
less perfect, but exceedingly useful one was discovered by Miss Anning, 
at Lyme Eegis, . . . now in the British Museum. Also portions of the jaws 
of a very large kind have been discovered in our Chalk formation, ith 
other bones, now supposed to have belonged to a similar animal. From 
these specimens we learn that the animal was a true Saurian, apparently 
adapted for flight and for arboreal and terrestrial movements, and instead 
of possessing, like the bat, an extension of all the fingers, it had only one 
prolonged, the others being used in progression. . . . We may suppose that 
the Pterodactyle in some degree in the use of its limbs approached the 
frog ; we may also . . . that the muscular development of the fore arm of 
the Pterodactyle was something between that of the bat, frog, and bird. 
The presence of quills in the bird has evidently materially afibcted the 
muscular development of the fore-arm ; as also their being bipeds involved 
a greater develo])ment of the muscles of the leg. . . . In the Pterodactyle 
the strain upon the bones of the wing would be principally in tlie long 
direction, there being no lateral pressure from feathers being attached to 
the bone. In the bird . . . the Haversian tubes vary according to the 
shape and uses of the wing, but there is no reason to suppose that such 
variations would be required in the Pterodactyle. In the Phalangers they 
extend longitudinally ; we may therefore suppose that such was the case 
in the Pterodactyle. . . . 
" iS'ext, with regard to the lacuna?, of what shape would analogy teach us 
to expect them to be in the Pterodactyle ? Surely long pointed ovals ; as, 
indeed, they have been so figured, only the mistake made was in supposing 
such a shape was peculiarly characteristic of the Pterodactyle, whereas the 
shape of ihelacuna is characteristic of no class or order of vertebrate animals, 
