PECTORAL SKELETON OF TELEOSTEANS. 379 
The “Interclavicle: 
This bone was first described in the stickleback by Parker, 
and because of its resemblance to the true clavicle (inter- 
clavicle) of the sturgeon he called it “ interclavicle.” 
Recently Starks has disputed this decision, and after a careful 
study of the pectoral skeleton of Hemibranchii has come tothe 
conclusion that this bone has no separate existence, but is 
only an extension of the coracoid (hypocoracoid). A glance 
at Pl. 23, fig. 12 shows him to be wrong in this conclusion 
for there it will be seen that the “interclavicle”’ is quite 
separate from the coracoid. 
This reopens the question of its homologies once more. 
This bone is related to the post-coracoid process, which, as 
we have seen, very probably represents the metapterygium. 
Now the “ interclavicle” of the sturgeon is related only to the 
lower tip of the coracoid (PI. 28, fig. 15, co.), and does not come 
near the metapterygium. ‘The two bones, therefore, are not 
homologous, and the “interclavicle” of Gasterosteus and its 
alliesshould be called bya different name, viz. “ infracleithrum.” 
Mr. Regan has called my attention to the presence of a 
similarly placed bone in Eurypholis (Woodward, p. 207). 
There can be little doubt that it is an infracleithrum also. 
SUMMARY. 
1. The earlier stages in the development of the pectoral 
skeleton of the salmon are fundamentally the same as those 
of the stickleback (p. 370). 
2. The mesocoracoid appears late in the development of 
the salmon, and is associated with the rotation of the glenoid 
border into a transversely horizontal position (p. 368). 
3. There is no sign of a mesocoracoid during development 
in the stickleback, and this is associated with the rotation of 
the glenoid border into a vertical position (pp. 370 and 371). 
4, Those Teleosts without a mesocoracoid probably consti- 
