294 
MIALL : BONES OF CTENODUS. 
tended obliquely downwards and forwards on the outside of the 
suspensorium, while the expanded plate defended part of the side 
of the head. The squamosal is the bone marked "d" in .Br. Giin- 
ther's figures of the skull of Ceratodus. 
This is all that I can positively or even probably identify as 
belonging to the skull proper, omitting the inferior arches, of 
Ctenodus. Fragments believed to belong to the interior of the 
skull exist, and require attention, but so far their connection with 
Ctenodus requires to be established, and their anatomical features 
are not elucidated. 
Mandible. The splenial and angular elements of the lower 
jaw have been well figured by the late Mr. Atthey, to whom we 
are indebted for some first-rate work upon the vertebrates of the 
coal measures. Examples are plentiful in the collections sent me 
Fig. 3. — Ctenodus obliquus. Left mandible . A, splenial with tooth. 
B, angular, x j. 
for examination. The inner piece or splenial (" dentary " of some 
authors) carries the tooth, and apparently unites with its fellow in 
a broad and firm symphysis. I find hitherto no indication of a 
separate dentary bone, such as Prof. Huxley has pointed out in 
Ceratodus, and Dr. Traquair in Dipterus. The angular bone 
( 14 articular " of some authors) lies along the outer surface of the 
jaw, and was doubtless separated from the splenial in Ctenodus, as 
in Ceratodus, by a cavity lodging Meckel's cartilage. A row of 
nutrient foramina (seen in the figure) marks the outer surface ; the 
pointed end is anterior. The best examples of the mandible which 
B 
