12 ON THE STRUCTURE OF EUSTHENOPTERON 
descending obliquely downwards and backwards, slightly bent a 
little below the middle, at which point there is a process for artic- 
ulation with the operculum. The hyomandibular resembles very 
much its homolog in the Palaeoniscidae. I have not noticed a 
foramen in this element. This and the quadrate are well shown 
on Plate 4. I have seen no specimen in which I could positively 
identify a sympletic, although it may have been present. 
On the ventral surface of the head there is a pair of large con- 
spicuous principal gulars in contact with each other for a portion 
of their length, but divided anteriorly by a narrow median gular. 
The principal gulars are figured on Plate 6, fig. 2, where the 
median gular has disappeared but the flanges for its reception are 
clearly shown. The principal gulars which are much narrower 
than their homologs in Holoptychius (cf. Plate 11, fig. 1), are 
bordered externally by a row of lateral gulars. These are rarely 
to be seen in the fossils. In the specimen figured on Plate 3 they 
have been mostly destroyed, but their position is indicated by the 
gap and flanges between the mandibles and the principal gulars. 
They are six in number, expanding gradually toward the rear. 
The clavicles are inserted between the posterior expanded por- 
tions of the principal gulars. 
The sensory canals on the head of Eusthenopteron are not 
nearly so conspicuous as in other members of the family, nor do 
they correspond in position entirely with those of Osteolepis, Dip- 
lopterus and Holoptychius. A transverse canal arising at a point 
near the suture between the parietals extends across the skull on 
each side, traversing the parietal and supratemporal and disap- 
pearing near the upper margin of the squamosal. From this 
canal a short branch arising near the inner margin of the parietal 
leads diagonally backward in the direction of the operculum. 
There is a short horizontal canal just below the nostril on the 
premaxilla and another extending across the upper limb of the 
preoperculum. A short canal crosses the quadratojugal and 
another extends diagonally downward and forward traversing 
the posterior splenial of the mandible. The lateral line is con- 
spicuous in many of the better preserved specimens. It arises 
near the upper border of the operculum and curving gently down- 
ward soon takes a horizontal direction along the middle of the 
trunk. 
There are a number of specimens in the Buffalo Museum which 
