VERTEBRATA. 419 
The girdles in a general way usually present three parts, 
cartilaginous in lower types, bony in higher. These are the 
following :— 
PECTORAL GIRDLE, PELVIC GIRDLE, 
Antero-ventral. Precoracoid. Pubis. 
Postero-ventral. Coracoid. Ischium. 
Dorsal. Scapula. Tlium. 
Cavity for articulation Glenoid. Acetabulum. 
of the limb. 
Although these two girdles can be thus directly com- 
pared, they become very dissimilar in higher types. The 
pectoral girdle has a membrane-bone, the clavicle, which 
replaces the precoracoid. This joins the sternum, and 
hence the pectoral girdle becomes connected ventrally with 
the axial skeleton; but in the pelvic girdle the dorsal 
element or ilium becomes attached to the vertebral column, 
forming a sacrum, and the pubes and ischia tend to fuse 
ventrally. 
The limbs are in most Pisces formed on the type called 
ichthyopterygium, consisting of one or more basal pieces 
(f. Skate) bearing a row of distal elements or fiz-rays. (See 
fisces.) In the other Vertebvata the limbs are of the type 
called a cheiropterygium or pentadactyle limb. In describ- 
ing this type we may first explain the following terms :— 
Both limbs in their supposed primitive position hang 
down on either side of the body, and if we draw an 
imaginary axis down the centre of the limb, certain parts 
of the limb are nearer the head, these being termed jve- 
axial, whereas those nearest to the hind-end of the animal 
are called postaxial, Again, the part of the limb which is 
closest to the body is termed the proximal end and the 
part furthest away the dzsta/ end, and generally any point 
described as dista/ lies further out than one called proximal. 
The typical cheiropterygium has a single proximal limb- 
bone, called in the fore-limb the Aumerus, in the hind-limb 
the femur. Then follow two distal limb-bones in each case ; 
the preaxial is the vadzus in the fore-limb, the “za in the 
hind-limb; whilst the postaxial are respectively the wna 
and the jidu/a. The small bones which follow are the 
carpalia or wrist-bones and the ¢arsafa or ankle-bones. 
