174 
PEOF. D. M. S. "WATSON AND MR. E. L. GILL ON THE 
surface of these flattened bones, as well as by the curve actually shown by the 
least crushed examples — among them some very small pterygoids which by 
their minuteness have escaped the worst of the crushing. 
The facet on the ," toe " of the pterygoid was remarked upon by Miall 
(1881, p. 292). It is precisely like the corresponding facet in Ceratodus, 
except that in Ceratodus the facet itself is composed of cartilage; and 
it doubtless had the same function, namely to support the quadrate and 
strengthen the articulation of the lower jaw. 
The Quadrate. 
The bone which we take to be the quadrate has long been known as a 
bone of Sagenodus, but has been assigned to' various positions. Fritsch 
Fig. 9. 
Sagenodus. Parasplienoids, X about h. 
A and B, palatal surface (B, the commoner type) ; C, dorsal surface. 
usually identified it as a scapula (" Schulterblatt "), as in his Taf. 77,^ 
figs. 1' and 4 (1889), but another example, Taf. 77, fig. 12, is labelled 
"Femur?". The same bone was well figured by Williston (1899, pi. 28, 
fig. 3), who suggested that it might be the ceratohyal. It is a large. 
bone in proportion to the size of the head, but in a Dipnoau with a 
head deep enough to accommodate such an operculum as that of Sagenodus 
the quadrate would necessarily be large. Even as it is, there is evidence 
that its upper end was incompletely ossified. The ossification of the rest 
of the bone, too, was more or less superficial,- though carried much further 
than in the quadrate of Ceratodus. As they are found in the shales, the 
bones have always collapsed under pressure as the core of cartilage decayed. 
