HAMMER-HEAD 



405 



variable of all the toes, and its taxonomic value is very limited. 

 In Hesperornis (Odontornithes), the Spheniscidie (Penguin) and 

 Steganopodes it is turned forward, and joined to the second 

 digit by a web, as is also the case to a certain extent in the 

 ColymUdai (Diver). In some of the Cypselidx (Swift) all four 

 toes are directed forward, but they are free at the base ; and in 

 certain of the Caprimnlgidie (Nightjar) and in the Goliidse (Mouse- 

 bird) the Hallux is reversible. In the Tubinares and the " three- 

 toed " Woodpeckers {Pkoides, Sasia and * Tiga) it is reduced to 

 a small subcutaneous nodule ; and in most LiMicOL^E, though visible, 

 it is in a scarcely functional condition, while in some of them, as 

 Calidris (Sanderling) and many Charadriidx. (Plover), it is wholly 

 absent, as it is also in the Alcidx. (Auk), Otididie (Bustard) and all 

 the existing Ratit^ except Apteryx (Kiwi). In Rissa (Kittiwake) 

 its condition varies almost individually from being nearly functional 

 to absence (see ToEs). 



HAMMER-HEAD or HAMMER-KOP, names given in the 

 Cape Colony to the Scopus timbretta of ornithology, called by 





// 



Hajmmer-head, Scopxis xvmbretta. 



Pennant and some writers the "Umbre." This was discovered by 

 Adanson, the French traveller in Senegal, about the middle of the 

 eighteenth century, and was described by Brisson in 1760. It has 

 since been found to inhabit nearly the whole of Africa and 



