10 ON THE STRUCTURE OF EUSTHENOPTERON 
and the supratemporal, is a small bone which has also been ob- 
served in Holoptychius and Glyptopomus. This evidently rep- 
resents an imperfect development of the transverse series of small 
quadrangular bones which in Osteolepis macrolepidotus, as shown 
on Plate 6, fig. 1, cross the skull immediately behind the parietals 
and supratemporals. Dr. Gregory (1915, p. 329) in his discussion 
of these elements has given excellent reasons for declining to con- 
sider them as homologs of the transverse post-parietal series in 
the Stegocephali and with this opinion I am inclined to concur. 
It is very difficult to make out the individual bones on the ex- 
ternal surface of the mandible as the sutures are mostly closed. 
However, after examining a very large number of specimens, I 
believe that I am safe in representing them as in Text fig. 3. The 
derm-articular appears on the outer surface as a narrow strip of 

Text fig. 3. Eusthenopteron foordi, Whiteaves. Ramus of lower 
jaw in a, inner aspect; b. outer aspect. Ang., Angular; A. Sp., Anterior 
Splenial; Cor., Coronoid; D. Art., Derm-articular; D. Dentary; F., Fossa 
for adductor mandibulae; Hym., Hyomandibular; P. Sp., Posterior Sple- 
nial (above which is a large mandibular vacuity) ; Qu., Quadrate. 
