708 



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



Sternum, plnin in outline, is produced ; in birds that hop and run 

 more than they fly, long, thin processes are seen for the attachment 

 of certain abdominal muscles, hut the rest of the sternum is not filled 

 up, so that we have a very short sternum with complicated processes. 

 In proof of this, contrast the sternum of the Gull, in which the two 

 pairs of lateral processes, which afford attachment to the end of the 



Fig. III. 



1, 2, 3, posterior outline of the sternum in TroccUaria fiigantca, Biomedca exti- 

 lans, and Crax alhcrfi ; tlie sliaded part is very lliin, and flie presence of 

 a siniilnr tbin margin on llie flattened ribs of the last-named conelusively 

 sbows that tbis mai'pin results i'rom a process of addition. 4, sternum 

 of Didmimhis, 5, of Hcs2:)CTornis (cast), showing posterior lateral process ; 

 the last sliows, like Casiiarius, Bfica, and fig. 9, Plate XLII., an incom- 

 plete fusion, probably due to the same causes that have operated in 

 ■widening tlie sternum during the establishment of the Avian type. (All 

 CO., reduced.) 



a, b, c, sterna of 8 and 9 clays' Chicks: «, shows abnoimal persistence on the 

 right side of rudimentary 8th rib attached to the Tib; b and c, dorsal 

 and ventral aspects of sternum, showing incomplete keel and absence of 

 median furcular apophysis. 



large pectoralis major, are scarcely seen to project from the sternum, 

 with the sternum of the Fowl or Tinanius, in which the long 

 processes afford attachment merely to a few thin fibres of that 

 muscle. Sterna of the Common Duck shoT? much variation, with a 

 tendency to fill up the sternum. The sternum of the Gull (cf. 

 Plate XLIII. figs. 9 and 10) shows how the jjrocess of filling up 

 takes place. la all the specimens examined except the one figured, 

 the two processes were distinct, even iu the earliest stages examined ; 



