PECTORAL SKELETON OF TELEOSTEANS. 377 
Attention has already been drawn (p. 369) to the close 
relationship which exists between the presence of a meso- 
coracoid and the horizontal rotation of the glenoid border. 
If the facts of development are any guide at all, it is very 
Fic. 2.—Diagram of pectural skeleton of Acipenser. g. Girdle. 
g.7. Radial elements belonging to the girdle. m¢. Metaptery- 
gium. mt.7. Radial elements belonging to metapterygium. 
m1—5. First five spinal nerves. 
difficult to see how the type of girdle without a mesocoracoid 
has been derived from that with a mesocoracoid, and vice 
versa. In the development of the former there is no sign of 
Fic. 3.— Diagram to illustrate the movements of the glenoid line 
during development. (1). Primitive position parallel to long 
axis of the body. (2). Final position in the salmon. (8). Final 
position in the stickleback. 
a vanishing mesocoracoid or of an inwardly moving glenoid 
border. 
In the most recent classification of Teleosts (Boulenger) all 
the non-ostariophysous fishes with a mesocoracoid are placed 
in the sub-order Malacopterygu. The lowliest forms without 
