524 [April 5, 
Cope. ] 
TRIMERORHACHIS INSIGNIS. Gen. et sp. nov. Ganocephalorum. 
See American Naturalist, May (April 22), 1878, p. 328. 
This genus is referred to the Ganocephalw of Owen, as a Stegocephal 
Batrachian with vertebral centra represented by separate cortical ossifica- 
tions, and with the chorda dorsalis persistent in the basioccipital region. 
The basioccipital bone, although ossified, supports no condyles properly so 
called, but a cup-like articulation for the first vertebra, like that of fishes, 
but which is perforate for the chorda dorsalis. It possesses the other char- 
acters of the suborder in the presence of zygapophyses and of the quadrato- 
jugal arch. 
Char. Gen. The centrum is represented by three cortical ossifications of 
the chorda-sheath, a median inferior, and two lateral. The lateral pieces 
are quite distinct from each other, and are in contact with the neurapoph- 
yses above, and the posterior border of the median segment in front. 
The neural arch joins chiefly the lateral elements, but is in slight contact 
with the lateral summits of the inferior element. The halves of the neural 
arch are codéssified, and support well developed zygapophyses, but no neural 
spine. A lateral expansion of the base of the neurapophyses represents the 
diapophysis, but it is horizontal and thin. ; 
The cranial bones are sculptured with pits and reticulate ridges. The 
parasphenoid bone is flat. The external nostrils are large and superior, 
and not anterior. The angle of the mandible is little produced, and the 
glenoid cavity is transverse and wider at the inner than the external ex- 
tremity. The inner wall of the mandible descends from the glenoid fossa, 
including with the horizontal outer wall, a deep internal pterygoid fossa. 
No corenoid bone or process. Symphysis short. 
The teeth exhibit the inflected dentine of this and allied groups. So far 
as preserved, they are simply conic, but there are none with the apices 
complete. There are two series on each side of the upper jaw, both of 
which consist of larger teeth at their anterior portions. The anterior teeth 
of the inner row beneath the external nares, are much the largest. A thin 
bilateral bone from some part of the roof of the mouth supports some large 
teeth, and a row of small ones diverging from them on each side. The 
mandibular teeth are in one principal series, and become a little larger an- 
teriorly. Near the symphysis there are on each side, within the external 
row, one or two large teeth. The ribs are short and little curved, and 
they have flat expanded heads. They are attached to the diapophysial 
expansion of the neural arch. Such limb bones as are preserved are with- 
out condyles, and are of relatively small size. 
Trimerorhachis differs from Archegosaurus in the ossification of the 
basicranial elements ; in the absence of attached neural spines, and in the 
regular and definite tripartite ossification of the chorda-sheath. The form 
of the cranium of Trimerorhachis is unknown. 
Char. Specif. There are two large tusks at the anterior extremity of 
the inner’superior row of teeth, and two similar ones on the plate-like ele- 
ment above described. The inferior border of the mandible rises gradually 
posteriorly to below the posterior border of the glenoid cavity, behind 
