BUFFALO SOCIETY OF NATURAL SCIENCES 11 
bone wholly covered by the quadratojugal. Below this is the 
angular which is followed in front by a large posterior splenial ; 
and in advance of this the lower border of the jaw is completed 
by two narrow bones, the anterior splenial and the infradentary. 
These two bones can easily be made out on a pair of large man- 
dibles belonging to the New York State Museum figured on Plate 
3, although they are not conspicuous in the photographs. They 
are also to be observed in inner and outer view on the mandible 
figured on Plate 7. The dentary is a long bone expanded in front, 
narrow behind, its upper border studded with minute teeth. 
On Plate 11 I have figured an interesting specimen of Holop- 
tychius quebecensis, Whiteaves, which displays in inner view the 
principal and lateral gulars together with a pair of imperfect man- 
dibles. Only the outer bones of the mandible are preserved, but 
these confirm, to a great extent, the structure of the mandible of 
Eusthenopteron; and Dr. Hussakof and I (1918) have recently 
figured a mandible of the remarkable Crossopterygian, Onychodus 
which indicates a somewhat similar arrangement. 
The inner surface of the mandible being destitute of ornament 
is much more easily made out. Lying within and below the margin 
of the dentary there is a series of coronoid bones studded with 
minute teeth and supporting a row of large tusks. The posterior of 
these bones is the longest and terminates behind in a process which 
articulates with the quadrate and is separated from the preartic- 
ular by a large fossa for the aductor mandibulae. The preartic- 
ular is also in contact with the quadrate and is notched anteriorly 
to receive the elongated posterior splenial. The angular appears 
as a narrow strip of bone at the posterior lower margin of the jaw. 
Above the posterior splenial is a large mandibular vacuity. The 
anterior splenial and infradentary complete the lower margin of 
the jaw in front. There is a small foramen just above them. 
The mandible of Eusthenopteron thus shows a most striking 
and remarkable resemblance to that of a primitive amphibian, for 
instance that of the Stegocephalian Trimerorhachis, even to the 
position of the various foramina; a resemblance which is further 
heightened as I shall later show by the minute structure of the 
teeth. 
The quadrate is a small bone lying in the angle of the jaw, rather 
thick behind, over-lapped externally by the hyomandibular, which 
is an elongated bone somewhat expanded above, cylindrical below, 
