232 



MR. P. CHAL^EES MITCHELL ON SO-CALLED 



run down each digit. "Where the digit-scutes come in contact 

 with the other series, they mav run down parallel with them and 

 appear on the distal edge o£ ihe tarsus. In the arm of a lizard 

 (fig. 7, B) the interference is more strikingly apparent, there 



:Fig. 7. 



1 2345 



A. Foot of a Passerine bird. B. Hand of a Lizard. C. Diagram of scales or 

 feathers on a hypothetical ancestral bird's wing. The quills of modern 

 birds are represented by darker spots. 



being along the distal edge five scales which are in series with 

 the digital rows, and there is an abrupt transition from these 

 transverse rows to the modified digital rows. In fig. 7, C 

 represents diagrammatically a simple mode of feather-distribution 

 on a pentadactyle wing which would result in a gap. Eows run 

 along the digit?, and where these meet the transverse rows a 

 wedge-shaped piece is intercalated, forming the transition. I 



