CLAKIS—CLA WS 89 
CLAKIS, a Scottish name for the BERNACLE. 
CLAMATORES, the third Order of Birds according to the 
arrangement of Andreas Wagner (Arch. fiir Naturgesch. 1841, ii. p. 
93), in which he included all the PicaARL& of Nitzsch which were 
not ZYGODACTYL or AMPHIBOLIC. Subsequently Prof. Cabanis 
(op. cit. 1847, 1. pp. 209-256, and ii. pp. 336-345) gave in greater 
detail the Families, subfamilies, and genera which he believed the 
“Order” should comprise, and his are the views which have been 
_ adopted by most of the systematic writers who have recognized it. 
CLAVICLES (Lat. clavicula, the collar-bone). Each clavicle 
articulates by its dorsal end with a process on the median side of 
the dorsal end of the coracoid, or with the scapula, or with both ; 
the ventral ends of the two clavicles generally fuse with each other, 
forming the FURCULA, and approach the anterior end of the crest 
of the sternum. Between them the CGisopHAGUS and the TRACHEA 
pass from the neck into the thoracic cavity (see SKELETON). 
CLAWS or NAILS are the horny sheaths of the terminal 
phalanges of the toes and fingers, generally curved, and often 
sharply pointed. They are produced by a thickening of the Mal- 
pighian layer, which forms the “ nailbed” out of which the corneous 
cells grow. The toes of most birds are protected by claws or flat 
nails, only in the Ostrich the outer toe has no nail, or hardly 
any, but the often reduced hallux is frequently unprotected. The 
inner side of the nail of the third toe is often serrated like a fine 
comb, as in Cormorants, Herons (including Scopus), Ibis, Dromas, 
Cursorius, Glareola, also in many Nightjars ; in Podicipes the distal 
margin of the third nail is serrated. 
Nilsson, Meves, Stejneger, Collett, and Malmgren (cf. Dresser, 
BL. Eur, vii. p. 189, pl. 485) have described the periodical shedding 
of the claws in Lagopus, which grow to a considerable length during 
winter, the seasonal extension dropping off in spring as do the 
- horny fringes on the toes in the Black Grouse, Capercally, and allied 
birds. 
Claws on the tips of the fingers are much rarer. Archzopteryx 
had a well-developed hooklike claw on each of its three fingers. In 
recent birds such claws are restricted, when occurring at all, to 
the pollex and index, being sometimes surprisingly well developed, 
although hardly functional. They occur more or less regularly on 
the first two fingers in Struthio and Rhea (occasionally as embry- 
onic traces even on the third finger), also in Anseres and Birds-of- 
Prey (e.g. Milvus and Cathartes). A pollex claw alone has been 
found in various Anseres, in Gallus, Birds-of-Prey (especially well 
developed in the Kestrel), and individually in the Whitethroat 
and in the Blackbird.! An index claw alone occurs in Casuarius, 
1 Such an example of the Whitethroat is in Mr. Seebohm’s collection, and 
