MACKIE — ON" FOSSIL BIRDS. 



21 



birds. It seems therefore possible, from the 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 longitudinal, braced more or less, because that would 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 Pterodactyles. It must not, however, be forgotten that 

 we are quoting an author who was 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 Pterodactylus longirostris perhaps affords us the most perfect 

 means of studying the singular proportions of its skeleton. A larger and 

 less perfect, but exceedingly useful one was discovered by Miss Anning, 

 at Lyme Hegis, . . . now in the British Museum. Also portions of the jaws 

 of a very large kind have been discovered in our Chalk formation, with 

 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 affected the 

 muscular development of the fore-arm ; as also their being bipeds involved 

 a greater development of the muscles of the leg. ... In the Pterodactyle 

 the strain upon the bones of the wing would be principally in the 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 Phal angers they 

 extend longitudinally ; we may therefore suppose that such was the case 

 in the Pterodactyle. . . . 



" Next, with regard to the lacunse, 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 the lacuna is characteristic of no class or order of vertebrate animals, 



