610 MUSCULAR SYSTEM 
leg ; but these four principal modifications are linked to each other 
by intermediate stages, which moreover frequently occur in closely- 
allied genera or even species. Thus the caudal head is very weak 
in (Edicnemus superciliaris and (. bistriatus and, as Garrod found, 
does not exist in @. grallarius. Dicholophus cristatus, like Otis, has 
lost it, but D. burmeisteri the iliac head as well. In Ciconia, the 
Striges and Cathartidx the whole muscle is represented only by the 
feebly-developed caudal head, and in Leptoptilus this also is lost. 
In some of the Limicolx, for instance Charadrius pluvialis and Vanellus 
cristatus, the presence of the iliac head is an individual variation. 
In Pedionomus the iliac head is very large, while the caudal is 
reduced to a very thin and feeble slip that does not even reach the 
femur, but merges into the iliac: if this reduction were continued 
Pedionomus would agree with Pavo and Meleagris and not with 
Turniz, in which the iliac head is absent. Thus the taxonomic 
value of this muscle may be judged from the following table, 
shewing its four principal modifications :— 
Passeres 
- 
Caudal and Iliac Head Caudal Head alone Iliac Head alone Both Heads 
present. present. present. absent. 
Ratiti 
Tinamidee 
Pedionomus Turnix 
Gallinz (most) Pavo, Meleagris 
Pterocles 
Columb (most) Lopholemus 
Glareola 
Numenius Scolopacinz (most) 
Hematopus Tringine 
Himantopus Strepsilas 
(Edicnemus  super- Ci. grallarius 
ciliaris, . bistri- 
atus 
Charadrius Otis 
Vanellus Eupodotis | 
Crex Grus 
Parra Dicholophus — cris- | D. burmeisteri 
tatus ; 
Sterninee Larine 
Aleidee 
Ibididee Ciconiinee Phcenicopterus Leptoptilus 
Platalea Herodii 
Tubinares Steganopodes 
Colymbus Podicipes 
Spheniscidee 
Anatide Accipitres Serpentarius 
Striges 
Psittaci 
Centropus Pici 
Cypselomorphze 
