THE PECTEN AND ITS ANALOGUES 



649 



a pecten exemplified by that of the ostrich, Struthio camelus (Fig. 

 192a). Here the organ has a central vertical panel which is buttressed 

 along its sides and ends by lateral vanes (Fig. 192c). The same plan 

 is followed by the 'American ostrich' (Rhea) and apparently by the 

 tinamous. The situation in the emu (Dromceus) is unknown; but in the 



Fig. 192 — The peaen. 



a, peaen and optic disc of ostrich, Struthio camelus. x5. After Franz. 



b, portion of eyeball wall bearing pecten of domestic fowl, exemplifying type present in 

 most birds. x8. After von Szily. 



c, section of a near, and parallel to, its base, showing central web and lateral vanes. After 

 Franz. 



d, section parallel to base of pecten of red-tailed hawk, Buteo b. horccilis, showing pleated 

 structure characteristic of the common type of pecten shown at b. x7. 



b- 'bridge' which cements folds distally; d- dorsal end of peaen. 



