176 
PROF. D. M. S. WATSON AND MR. E. L. GILL ON THE 
the Hancock Museum, there is a small angular with the " dentary " still 
in natural articulation with it. This specimen bears a label in Atthey's 
handwriting, and as he called it simply " Ctenodus, articular bone,'" he 
presumably thought it merely a damaged or aberrant angular. It is 
represented in fig. 14, p 180. 
The figures here given will make it unnecessary to describe the jaw at 
length. Restorations in different aspects are given in fig. 12, A, B, C, D, 
p. 178, and corresponding views of the lower jaw of Ceratodus, after removal 
of the cartilage, are given in fig. 13, p. 179. It will be seen that apart 
from the difference in the tooth-plates the two jaws are remarkably alilce. 
The bones in Sagenodus are very much stouter, but that is a difference that 
obtains in nearly all parts of the skeleton. 
Fig. 10. 
Saffenodi(s. Eeconstruction of palate, showing pterygoids in natural 
articulation with the parasphenoid. The postero-lateral wings 
• (quadrate rami) of the pterygoids are shown flaltened into 
the same plane as the parasphenoid. 
The bones that differ most in the two forms are tlie " dentaries," for 
though they are much alike as seen from below, the " dentaries " in 
Sagenodus take a more essential share in forming the jaw than they do in 
Ceratodus. In the latter fish they are papery bones feebly connected with 
the angulars by a very slight groove near tlie edge. In Sagenodus (fig. 15, 
p. 180) they are strong bones firmly united with the angulars, which have a 
pronounced groove for their reception along the anterior half of their lower 
edge. But the most striking difference in the " dentaries" of the two fishes 
