74 ANATOMY OF VERTEBRATES. 



about the middle of the ' medius ' metacarpal. This supports two 

 phalanges, fig. 19^ 5, 5: the proximal oue singularly expanded by 

 a lamelliform growth from its whole ulnar side, excavated out- 

 wardly for the attachment of primaries: the next phalanx is 

 smaller and ends in a point. The ' annularis ' metacarpal supports 

 a short and slender pointed phalanx, which in the Frigate-bird is 

 closely joined, length^vise, to the contiguous expanded phalanx 

 of the mid-digit. 



The hand-segment is the longest of those of the pectoral limb 

 in Swifts and Humming-birds: exceeding by three times the 

 length of the humerus : and the bones have a proportionate thick- 

 ness. The mid-metacarpal shows a series of large impressions 

 for the distal * primaries ' in Rajytores, and also a longitudinal 

 tendinal groove on the anconal side. The metacarpal, fig. 19, r, 

 and phalangeal, ib. 5, t, bones, in the Penguin are flattened, like 

 the antibrachial bones. 



The index digit in Struthio and the medius digit in Apterijx, 

 support each their claw. The claw or spur, when present 

 in other birds, e. g. Syrian Blackbird {Merula dactyloptera), 

 Spur-winged Goose {Anser Gamhcnsis), Knob-winged Dove {Di- 

 dunculus), Jacana {Parra Jacana), Mound-bird (Me(/apodius), 

 Screamer {Palamedca), is developed from the radial side of 

 the metacarpus or from the index digit. The Screamer has two 

 spurs, the homotypes of the metatarsal ones in Pavo hicalcaratus. 

 The claw upon the index digit of Archeopteryx was curved and 

 sharp ; and the remains of the unique example of this ancient 

 fossil bird make it probable that the hand had a second free 

 unguiculate digit, perhaps the homologue of the pollex.^ 



Although the instances of these weapons and the occasional use 

 of the wings in Birds not so armed, e. g. the Swan, show them in 

 the light of means of attack, the bones of the pectoral limb in 

 Birds are modified mainly for volant action ; the articulations 

 restrict the movements of the several segments to the service of 

 wings, and the processes for muscular attachments relate to such 

 development and disposition of the moving forces as flight requires. 



The larger feathers which overlie, in a series, the humerus, are 

 termed, in ornithology, ' scapularies : ' those still larger which 

 overlie or are attached to the ulna are the * secondaries ' or ^ wing- 

 coverts ; ' those which are attached to the manus are the ' pri- 

 maries,' they are the longest : a group of feathers attached to the 

 stunted index digit are the ^ spurious ' or ' bastard ' feathers. 



' XV. p. 39, pi. 2, fig. 1. 



