iv.] SKELETON OF UPPER LIMB. ' 161 



The clavicles may be fused together in the middle line, 

 as in the merrythought of Birds. 



The meso-scapular segment never appears to become very 

 large, but the pre-coracoid part becomes very considerable in 

 the Ostrich, where a foramen indicates the line of demarcation 

 between it and the true coracoid, and it is large in many 

 Lizards, e.g. the Monitors. In Chelonians the pre-coracoid is 

 a large bone descending from the glenoidal region down- 

 wards and inwards towards the ventral shield of the cara- 

 pace. It has been spoken of as a true clavicle, as also the 

 anterior of the two bars which, in the Frogs and Toads, pass 

 inwards from the scapula, but which seems to be really a pre- 

 coracoid. 



The last element, the omosternum, becomes amongst Mam- 

 mals very conspicuous in certain Shrews and Mice ; also in 

 certain tailless Batrachians, e.g. Pseudis and Pipa. It may 

 be that this element is the same as that next to be noticed, 

 and which otherwise has no representative in man. or in any 

 but the lowest Mammals. 



The element in question is the inter-clavicle, which is 

 enormous in the Monotremes, and forms the bulk of that large 

 T-shaped bone which prolongs as it were the manubrium ot 



FIG. 137. FRONT VIEW OF LEFT HALF OF SHOULDER-GIRDLE OF A GECKO 

 'LiZA.RDHemidcictylus. (After Parker.) 



f, curacoid ; cl, clavicle ; i, inter-clavicle ; me, meso-coracoid ; pc, pre-coracoid ; 

 j, scapula ; ss, supra-scapula ; st, sternum. 



the sternum, and which bears on its diverging arms the small 

 splint-like clavicles. The same element is more or less 

 similar in shape in many Lizards, e.g. Iguana and Monitor. 

 It may be cruciform, as in Cyclodus, or a simple forwardly 

 directed ossicle, as in the Crocodile, or a median expanded 

 lamella of bone or cartilage, as in Anguis and Chelonians. 



