STRUCTUKE OF FOSSIL BONE. 73 



the carpus, sends forth extremely fine tendons over the 

 convex surface of each of the fingers, terminating in the last 

 joint. In the pterodactyle, the digitus auricularis that forms 

 the wing, would seem to require proper extensors and flectors ; 

 and we may suppose that the pterodactyle, in some de- 

 gree, in the use of its limbs, approached the frog ; we also may 

 assume it possessed extensores carpi radialis and idnaris, 

 an extensor digitorum communis, also an extensor proprius 

 digiti minimi (auricularis), as well as flexores carpi radialis 

 and ulnaris, a flexor digitorum communis, a flexor proprius 

 digiti aiu'icularis, and possibly a pronator and supinator. The 

 bird, indeed, has two muscles which occupy the place of the 

 pronator teres, which are not used for pronation but flection. 

 We may therefore imagine that the muscular development of 

 the forearm 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 forearm ; as also their being bipeds involved a greater 

 development of the muscles of the leg, it would be, how- 

 ever, unnecessary to enter upon them. In the pterodac- 

 tyle, the strain upon the bones of the wing would be prin- 

 cipally in the long direction, there being no lateral pres- 

 sure, from feathers being attached to the bone. In the bird 

 the quill feathers are a very important element, and it has 

 been shown that the Haversian tubes vary according to the 

 shape and uses of the wing ; but there is no reason to sup- 

 pose that any such variations would be required in the ptero- 

 dactyle. In the Phalangers they extend longitudinally; we 

 may therefore suppose that such was principally the case in 

 the pterodactyle; we have every reason to conjecture this 

 from analogy. Take, for instance, the bill of the pelican, 

 which is long; how do they run? longitudinally; or the 

 tibia of a heron? longitudinally also; or in the spiculse or 

 shafts of bone that shoot across the interior of the humerus 

 of a goose, or in the ordinary coracoid of a bird, the same 

 dii'cction is observed. 



Next, with regard to the lacunje; 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 the supposing su^ch a 

 shape was peculiarly characteristic of the pterodactyle ; 

 whereas the shape of the lacuna is characteristic of no class 

 or order of vertebrate animals, but is only connected with 

 the requirements of the bones of the animal, and may be 

 long or round in the same animal as occasion requires.* The 



* Our common roach beautifully exhibits this. 



