PELVIC GIRDLE 2/ 



phalanges. The Hylidae, and many of the climbing members of 

 the Eanidae with adhesive discs, possess an extra skeletal piece 

 intercalated between the last and last but one phalanges of the 

 ringers and toes. This piece, a mere interarticular cartilage in 

 Hyla, is in the following Eaninae developed into an additional 

 phalanx, so that their numbers are 3, 3, 4, 4 in the hand and 

 3, 3, 4, 5, 4 in the foot : Cassina, Hylambates, Bappia, Mega- 

 lixalus, Rhacophorus, Chiromantis, Ixalus, and Nyctixalus. All 

 the other Eanidae are without this additional phalanx, irrespec- 

 tive of the presence or absence or size of digital expansions. 1 



The pelvic girdle looks like a pair of tongs (see Fig. 4, 

 p. 22). The ilium is enormously elongated and is movably 

 attached to the sacral diapophyses. This connection is always 

 pre-acetabular in position. The ilium and ischium co-ossify com- 

 pletely, and make up nearly the whole of the pelvis ; the pubis 

 is very small, and remains cartilaginous unless it calcifies. It 

 rarely possesses a centre of ossification, for instance in Pelobates, 

 where the osseous nodule is excluded from the acetabulum, 

 recalling certain Labyrinthodonta, whose ossa pubis likewise 

 do not reach that cavity. The latter is open or perforated in 

 young Anura and remains so in the Discoglossidae, but in the 

 others it becomes closed up as in the Urodela. The ventral 

 halves of the pelvis, besides forming a symphysis, closely approach 

 each other, just leaving room for the passage of the rectum and 

 the urino-genital ducts. 



The hind-limbs are in all cases longer than the fore-limbs. 

 The femur is slender, the tibia and fibula are fused into one bone. 

 The tarsus is much modified by the great elongation of the two 

 proximal tarsalia (there being no intermedium) into an astragalus 

 and a calcaneum, both of which fuse together distally and 

 proximally, or completely as in Pelodytes ; in the latter case the 

 limb assumes a unique appearance, since it consists of three 

 successive and apparently single bars of nearly equal length. 

 The other tarsal elements, especially the more lateral ones, are 

 practically reduced to pads. The Anura have thereby acquired 

 two well - marked joints, one cruro - tarsal, the other tarso- 

 metatarsal ; this shows a high stage of specialisation in com- 

 parison with the Urodelous and Stegocephalous type of still 

 undefined joints. 



1 Boulenger, P.Z.S. 1888, p 204. 



