sseminamed -_ — OL ee ee eee 
1922.]} Homology of W eberian Ossicles. 3 
The tripus is by far the largest ossicle. It has been homo- 
logised with either the transverse process of the third vertebra 
or its rib.' But I have found it to be a compound bone 
formed by the coalescence of three distinct elements. The 
drawings given ae from actual specimens illustrate this 
clearly. In fig. there is a distinct bony element (t.p.®) 
which runs from the dorsal aspect of the anterior process of 
CES. p. art. p. 

b re 
TEXT-FIG. pg el a compound bone. 
Same as seen from above. 
= me as seen from below 
rie Bags are not drawn from the same specim ; 
Ant.p. = Anterior process of tripus; t.p.3 = Per st process o of 
third macohen ari.p. = articular process of tripus; 7.4 = rib of fourth 
vertebra; cres p. = crescentic process of tripus; r.3 = rib of thi 
vertebra 
the tripus (ant.p.) to its articular process (art.p). Below the 
articular process it is separated from the main body of the 
ossicle by two cavities, which when followed in a large series 
of preparations, become gradually reduced and ultimately 
vanish altogether. Thus the two distinct elements at the 
anterior end become fused and indistinguishable. I am of 

1 Regan, Ann. Mag. Nat Hist. (8) VIII, p. 14 (1911) 
