1 62 ELEMENTAR Y ANA TOM V. [LESS. 



It may be small and serve to connect the clavicles, as in 

 Birds, where it forms the middle of the merrythought. It 

 may be very large and bifold, as in many Fishes, e.g. Cottus 

 and the Sturgeon. 



The true clavicle, more or less cylindrical or at least slender 

 in Mammals and Birds, may become expanded in Lizards 

 (e.g. Hemidactylus, Cydodus, and especially Trachydosaurus]. 



In Chelonians also the clavicles are greatly expanded and 

 Form the two foremost bones of the ventral part of the 

 carapace, the median one immediately behind them being 

 the inter-clavicle. 



1 



Fir,. 138. SCAPULAR ARCH OF A FISH Zens. (After Parker.) 



/> 4 , the fourth or lowest of the four brachials which together may represent the 

 humerus, and to which the fin rays are attached ; c, coracoid : cl, clavicle ; pc, 

 pre-coracoid ; //, post-temporal, which connects the scapular arch with the 

 skull ; si, supra-clavicle the bar of bone unmarked, which descends back- 

 wards, is the post-clavicle. 



The great size of the clavicle here and in Trachydosaurus 

 prepares us for the still vaster development of this part in 

 bony Fishes, where the clavicles become enormous, and may 

 not only be provided with a distinct inter-clavicle, but also 

 each with a distinct portion above the supra-clavicle (as in 

 the Dory, Zeus, the Sturgeon and others), and besides this 

 with a posterior element, a post-clavicle, as in the Dory, 

 Perch, and Cod. 



Thus the clavicle of man, instead of being the simple struc- 



