704 



MISS B. LINDSAY ON THE AVIAN STERNUM. [Juiie 16, 



correspond exactly with those drawn from actual specimens in dif- 

 ferent stages (see Plate XLIV.). 



It is to be clearly understood that the broadening median end of 

 the clavicle, which Gotte describes in its condition during the 8th 

 day of incubation, and interprets as an interclavicle, has nothing to 

 do with the broad median end of the triangular clavicle figured below. 

 The clavicle becomes uniforndy thin throughout its length toward 

 the close of the 6th day, as shown in diagram 3, fig. II. 



1, 2, 3, show cbanges in the shoiilcIer-gircUe of the Cbick, late on the 5th day of 

 incubation; 4, shows its condition during tlie 6tb day; and 5, its con- 

 dition late on the 6th day, when the coracoid bone has acquired its 

 sternal attachment and the coracoid and scapula have almost separated. 



The view above suggested with regard to the presence of a rudi- 

 mentary precoracoid in the Chick at a early stage, is borne out by 

 comparison of the condition of the internal part of the coracoid in 

 various types. 



Beginning with the Rati'se, "we see that where the precoracoid 

 is apparently lost, there seems to be a rudiment of it remaining in 

 the form of a process of the coracoid, situated in BroiiKBUs (Plate 

 XLIV. figs. 1.5 and IG) just beneath the clavicle. In Casuarius it 

 seems possible that the area of bone extending internally to the 

 foramen or incisura coracoidea^ is also comparable v^ith the precora- 

 coid, since in Struthio the said foramen is situated near the internal 

 margin of the bone; hut whether this precoracoid area is not rather 

 a new growth of the coracoid than the homologue of the Struthionic 

 precoracoid, is very uncertain. The peculiar marginal foramen seen 

 in Plate XLIV. fig. 7 is seen partly developed, occasionally, in the 

 Ostrich, where the precoracoid is present — a fact which supports the 



' This gives a passage to one of the nervi brachiales iiiferiorcs; this nerve 

 supplies the m. supracoracoideus (called pectoralis minor else-nhere throughout 

 this paper). 



