12 
other teeth in the length and diameter of its basal portion. From_its posi- 
tion it is probably an incisor. 
The anterior border of the orbit falls above the third tooth of the exter- 
nal row (counting from behind). The inner border of the maxillary bone 
is elevated into the ridge convex inwards, as in the other species of this 
family. The malar. base of the zygomatic arch is a moderately stout ver- 
tical oval. 
° Measurements. M. 
Length of dental series..... aihdcaseascon Soasie rey ane ese tns Gore wee 062 
Length of molar 6-8 series... ..... cece eee eee eee 029 
Width of the two molar series.............- cece ee eee . .009 
Vertical diameter malar bDone........ 0... eee eee eee .013 
The associated bones of the skeleton may belong to this or to the next 
species, or even to a small Hmpédocles whose teeth occur in the same lot. 
In the uncertainty of reference I do not describe them. 
FLELODECTES ISAACI Cope. Sp. nov. 
Founded on a fragment probably of a maxillary bone, lacking both ex- 
tremities, and considerably obscured by ferruginous deposit. : 
The characters are well marked, leaving no doubt that this species is 
distinct from those previously known. The bases of the teeth of one of 
the rows are much more extended transversely than those of the other, 
having the form of some of those of Hmpedocles. Asin that genus, they 
shorten anteriorly. In the fragment, I count on this row, bases of nine 
teeth. In the other row, I can only definitely count three, which are 
opposite the second, third. and fourth of the other series (counting from 
behind). They are wide transverse ovals, about half the long diameter of 
the posterior teeth of the other series. 
Measurements. M. 
Length of, bases of eight larger molars........+.--..+-- 032 
. P anteroposterior. ........e008 004 
Diameter of large molar ie ere tea -008 
Length of three smaller molars..... L@a wee pied seeaeee 912 
Long diameter of a smaller molar............6 cee e eens 004 
This species is dedicated to J. C. Isaac, the discoverer of the first species 
of this family. 
GANOCEPHALA. 
Examination of abundant material shows the correctness of my anticipa- 
tion (American Naturalist, 1878, 633), that the vertebree of the large batra- 
chian Zryops, would turn out to have the structure found in Rhachitomus. 
This genus then must be referred to the same sub-order as Trimerorhachis, 
and probably Actinodon Gaudry, which will be characterized by the seg- 
mented vertebral centra. If European authors are correct in stating that the 
vertebre of the Labyrinthodontia have undivided centra. the sub-order 
above mentioned must probably retain the name of Gunocephala, with ad- 
ditional characters. 
The identification of the scapular arch in Hryops, and of the pelvic arch 
‘ 
