THE PELVIC ARCH. 



31 



eomes divided by a ridge which grows out into a great crest 

 in Man and other Mammalia, and gives attachment to mus- 

 cles and ligaments. 



The ischium corresponds very nearly with the coracoid in 

 the pectoral arch ; the pubis with the precoracoid, and more 

 or less of the epicoracoid. 



The pelvis possesses no osseous element corresponding 

 with the clavicle, but a strong ligament, the so-called Pou- 

 partes ligament, stretches from the ilium to the pubis in many 

 Vertebrata and takes its place. (Fig. 14, Pp.) 



;flQ. 14 • 



-Side-view of the left Os Innominatum of Man: /^, ilium; 7a, ischium; Pp, publi 

 A^ acetabulum ; JPp, Poupart'B ligament. 



On the other hand, the m,arsupial bones of certain mam- 

 mals, which are ossifications of the tendons of the external 

 oblique muscles, seem to be unrepresented in the pectoral 

 arch ; while there appears to be nothing clearly corresponding 

 with a sternum in the pelvic arch, though the precloacal car- 

 tilage, or ossicle, of Lizards has much the same relation to the 

 isohia as the sternum has to the coracoids. 



Very generally, though not universally, the ilia are closely 

 articulated with the modified ribs of the sacrum. The pubes 

 and ischia of opposite sides usually meet in a median ventral 

 symphysis ; but in all birds, except the Ostrich, this union 

 does not take place. 



TJie Limbs of Fishes. — The limbs of Fishes have an endo- 

 skeleton which only imperfectly corresponds with that of the 

 higher Vertebrates. For while homologues of the cartilagi- 



