194 
PROF. D. M. S. WATSON AND ME. E. L. GILL ON THE 
Nevertheless we have little hesitation in regarding the bones shovi^n in 
fig. 28, p. 197, as the cleithrum and clavicle. Both are well represented in 
the Atthey Collection; from comparison with the corresponding bones of 
Sagenodus (fig. 17, p. 182), there can be no doubt that they are the cleithrum 
and clavicle of a Dipnoan ; and both reach too large a size to belong to any 
known form of Sagenodus. The cleithrum (fig. 28, A, p. 197) is found up 
to 7 inches (33 cm.) in length, the clavicle to at least 6 inches (30 cm.). 
The cleithrum differs from that of Sagenodus chiefly in having its hinder 
half (the upper part in A, fig. 28, p. 197) greatly thickened instead of 
Fig. 25. 
A C B 
CtenoiJus cristatns. Parasplienoid. 
A. Buccal aspect. B. Cranial aspect. 
C. Junction of disc and shaft in large examples. 
being strengthened by longitudinal ribs. Moreover, on its outer side this 
thickened portion has the character of a superficial bone, as though it had 
come to the surface under the skin behind the operculum as in D'qyterus, 
instead of being buried in muscle as in Ceratodus, and as it presumably was 
in Sagenodus too. 
The clavicle (fig. 28, B, C, p. 197), though it has the same essential 
structure as that of Sagenodus, diff'ers from it in having a longer articular 
head and a narrower and stouter shaft. We have found no specimens with 
