862 



SKELETON 



to the ischium. The proximal portion of the space thus enclosed 

 almost always forms a foramen^ called the J. ohturatum, because it 

 serves for the passage of the tendon of the m. obturator and the n. 

 obturatorius (page 625), which supplies that muscle, and the m. pub- 

 ischio-femoralis (page 611), or principal adductor of the thigh. The 

 rest of the opposed margins of ischium and pubis are connected with 



each other to a variable 

 extent, either by mem- 

 branes only or, if the 

 bones touch, by more or 

 less extensive ossification, 

 which in extreme cases, as 

 in some Anatidx, leads to 

 the obliteration of the 

 middle portion of the 

 shaft of the pubis, so that 

 its distal portion appears 

 in a prepared skeleton as 

 a separate bone. The dis- 

 tal end of the pubis is 

 mostly bowed inwards and 

 broadened, serving for the 

 attachment of the lateri- 

 ventral muscles of the tail 

 {m. pubo - cocajgeus). In 

 Siridhio only the end of 

 the pubis meets that of 

 the other side, forming a 

 dagger -shaped symphysis 

 upon which rests a great 

 part of the weight of the 

 abdominal intestines. The 

 spina pubica or anterior 



Pavo cristatus. 



COLYMBUS ARCTICUS. 



1. II. the Sacral Vertebne; 0.1-5, Cnual Vertebra. ; Cd. PJO^^^S of the OS publs 



l-5,Caudal;C^.i{;p.2,Capitularattachinentofthelast often Called the pectineal 



free ribs; Is. Ischiadic Vertebrae; I'.S. Postsacral A;/ p_ (350 fi*''. 4 p.) is 

 VertebrsB ; Rec.il. Iliac recess ; Tb. Tubercular part i i • 1 1 r i. 



of the rib. morphologically of great 



interest, because it is the 

 element which in Dinosaurs is described as the "pra3pubis," while 

 in recent Reptiles it is represented by the pubis proper, the 

 " pubis " of Birds being in reality homologous with the postpubis 

 of Dinosaurs and the processus lateralis pubis of other Reptiles. It 

 serves for the origin of the ambip:ns muscle (page 11), though 

 that not unfrequently extends to the adjoining part of ilium, or 

 further down to the shaft of the pubis, and hence has been 

 preserved when that muscle is present ; but the process is very 



