862 SKELETON 
to the ischium. The proximal portion of the space thus enclosed 
almost always forms a foramen, called the f. obturatum, 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 
Pr.pect. in some Anatidx, leads to 
the obliteration of the 
For.obt, Middle portion of the 
shaft of the pubis, so that 
its distal portion appears 
in a prepared skeleton as 
aseparate 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-coccygeus). In 
Struthio only the end of 
Pub. 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 
7 spina pubica or anterior 
PAVO CRISTATUS. COoLYMBUS ARCTICUS. . 
I, II. the Sacral Vertebree ; C. 1-5, Crural Vertebre ; Cd. Process of the oo pubis, 
1-5, Caudal; Cp. Cp.2, Capitular attachment of the last often called the pectineal 
free nee Ts. Ischiadic Vertebres ; IPS. RO (of. p- 650, fig. 4, ve) is 
Vertebree ; Rec.il. Diac recess; Tb. Tubercular part ee 
or thetibl morphologically of great — 
interest, because it is the 
element which in Dinosaurs is described as the “ prapubis,” 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 AMBIENS 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 
