206 
PROF. D. M. S. WATSON AND MH. E. L. GILL ON THE 
Our existing knowledge of the structure of the head still depends in the 
main on Pander's excellent description and figures. The only addition is 
Dr. Traquair's well-known restoration. 
One specimen (fig. 32), now in D. M. S. Watson's collection, shows the 
side of the head nearly perfectly. Its structure will be best understood 
from the figure; the interesting features are the relatively small number 
(seven) of circumorbitals, the presence of two small elements in the cheek, 
representing some part of the greatly-developed bones in this region in 
Osteolepids, and the presence of a very slender, toothless maxilla, lying below 
the orbit. 
Tig. 33. 
Clav. Cl'e 
Dipterus valenciennesi, Sedg. & Miircli. Ventral surface of bead. X 2. 
From a specimen in D. M. S. Watson's collection. 
Ang., angular ; Clav., clavicle ; Olbi., cleitlirum ; L.G. 1-3, lateral gulars, nos. 1-3; 
M.G., median gular ; Op., operculum; Po.Sp., post-splenial = preangular ; P.G.,, 
principal giilar ; S.Op., sub-operculum ; Sp., splenial. 
There is an indication of an inner ring of circumorbitals, already repre- 
sented in Dr. Traquair's restoration. 
This specimen shows the operculum and a section across the suboperculum, 
that bone having been driven outward and its upper half thereby removed 
in the counter slab when crushed down on the rigid clavicular arch. The 
sub-operculum is followed by a large principal gular, which supports a large 
lateral gular. 
In a triangukr space between these two gulars and the articular region of 
the lower jaw lie three small bones, which can only be lateral gulars. These 
little bones are also shown in identically the same form in the specimen 
No. 770, Hugh Miller Collection, Royal Scottish Museum. 
The gular apparatus is, however, best seen in the original of fig. 33, 
a small specimen crushed directly vertically and viewed from the ventral 
