38 THE ANATOMY OF VEKTEBEATED ANIMALS. 



in the i^ectoral arcli ; 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- 

 part's ligament, stretches from the ilium to the pubis in 

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



On the other hand, the marsupial hones of certain mam- 

 mals, which are ossifications of the tendons of the external 

 oblique muscles, seem to be unrepresented in the pec- 

 toral arch ; while there appears to be nothing clearly corre- 

 sponding with a sterniim in the pelvic arch, though the 

 precloacal cartilage, or ossicle, of Lizards has much the same 

 relation to the ischia 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 aU birds, except the Ostrich, this 

 union does not take place. 



The Idmbs 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 car- 

 tilaginous, and even of the bony, constituents of the pec- 

 toral and pelvic arches of the latter are traceable in Fishes, 

 the cartilaginous, or ossified, basal and radial supports of 

 the fins themselves cannot be identified, unless in the most 

 general way, with the limb-bones, or cartilages, of the other 

 Vertebrata. 



In its least modified form, as in Lepidosiren, the endo- 

 skeleton of the fish's fin is a simple cartilaginous rod, 

 divided into many joints; and articulated, by its proximal 

 end, with the pectoral arch. The Elasmobranchii possess 

 three basal cartilages which articulate with the pectoral 

 arch, and are called, respectively, from before backwards 

 — propterygial, mesopterygial, and metapterygial basalia. 

 With these are articulated linear series of radial cartilages, 

 upon which osseous, or horny, dermal fin-rays are super- 

 imposed. (Fig. 15.) 



