Vol 'i9W XV ] Clark, Tail-feathers and Coverts. 117 



5-8, 10 or 11. Toucan (Ramphastos cuvieri). This is the most 

 extraordinary case of supernumerary coverts, I have seen. As a 

 rule there are 10 or 11 major coverts in a single, distinct but 

 crowded series. In one individual however I found only 8 coverts 

 and it may be there is considerable individual diversity. Ordi- 

 narily there are two coverts over the base of rectrix 2, with none 

 over rectrix 1 ; covert 3 is between rectrices 2 and 3 while covert 

 4 is directly over rectrix 3; covert 5 is between rectrices 3 and 4, 

 while covert 6 is over rectrix 4; covert 7 again is between rec- 

 • trices 4 and 5, and covert 8 is over rectrix 5; coverts 9-11 are on 

 the corner of the pygidium, outside the rectrices. In the indi- 

 vidual with only 8 coverts, the indications are that coverts 1, 10 

 and 11 are missing. A further study of this remarkable toucan 

 is much to be desired. 



III. Coverts less numerous than rectrices. 



In every case examined, the reduction in the number of coverts 

 seems to take place at the outer end of the series, but it is possible 

 that in the Passeres and birds with a similar arrangement, covert 1 

 is wanting rather than simply displaced. In those unusual cases 

 where there are two coverts fewer than the rectrices, one of the 

 missing coverts is possibly no. 1. The question could probably 

 be answered by examination of large embryos or nestlings of the 

 Guinea-fowl or European Quail. 



5—4. Motmot (Baryphthengus ruficapillus) . 



6-5. Passeres. Psittaci. Kingfishers. Trogons. Some small 



hawks. Rails. 



6-4. Coturnix. Cyrtonyx. 



7-6. Coot. Gallinules. 



8-7. Lagopus. 



8-6. Numida. 



9-8. Pheasants. Bonasa. 



It will be seen from the above data, that relatively few birds 

 have more coverts than rectrices and these are chiefly natatorial 

 birds. Among land-birds, only the owls, the osprey and the big 

 toucan have supernumerary coverts, while of water-birds there are 



