ON THE CLASSIFICATION OF THE LABYRINTHODONTS. 185 
The age of the deposit from which Chalcosaurus was derived is still somewhat 
doubtful. Murchison refers it to the Permian formation. Eichwald, Ludwig, and 
Geinitz dissent from this view, and regard it as either Triassic or as intermediate 
between the Paleozoic and Neozoic epochs. Summaries of the evidence will be 
found in Naumann’s ‘ Geognosie,’ 2nd ed. p. 658, and in Von Meyer’s ‘ Palzonto- 
graphica,’ vol. xv. p. 98. 
Cocytinus, Cope. 
“ Vertebra and ribs osseous ; anterior limbs, thoracic shields, and abdominal arma- 
ture apparently wanting, Teeth on the premaxillary bone, none on the maxillary. 
Hyoid elements largely developed. An axial hyal with basihyal on each side, 
closely united with the corresponding ceratohyal, at the end of which is an element 
in the position of a stylohyal. Hemal or basal branchihyals three, the anterior 
two each supporting one pleural branchihyal, and the third supporting one also. 
The first or anterior hemal-branchihyal on the hemal side of the ceratohyal, ap- 
proaching the median line, and with elongate pleural element. Urohyal not seen.” 
C. GyRrnomes, Cope. 
Locality. Coal-measures, Linton, Columbiana County, Ohio. 
References. Cope, Proc. American Phil. Soc. 1871, p. 177.—Id. Supplement, 
p. 16. 
Colosteus, Cope. 
We fail to perceive any distinctive features of this genus. “The usual three sculp- 
tured pectoral bones are present. .... The abdominal region is protected by a series of 
scales which extend obliquely forwards to the medial line, where they meet, forming 
chevrons. ....Most of the teeth are coarsely incised sulcate for perhaps their basal 
half. .... The affinities are thus obviously to Apateon, and it is not beyond possi- 
bility that future investigations may prove it is the same.” 
C. scuTELLATUS, Newberry (= Pygopterus scutellatus, Newberry ; Colosteus crassi- 
scutatus, Cope). 
C. FOVEATUS, Cope. 
C. PAUCIRADIATUS, Cope. 
Locality. Coal-measures, Linton, Columbiana County, Ohio. 
References. Newberry, Proc. Acad. Nat. Sci. Philadelphia, 1856, p. 98.—Cope, 
Synopsis, p. 22.—Jd. Supplement, p. 15. 
Dictyocephalus, Leidy. 
The posterior part of the upper surface of the skull is known. Dr. Leidy remarks 
that in the arrangement of the cranial plates Dictyocephalus bears considerable 
resemblance to Trematosaurus. A radiate sculpture is conspicuous. The parietal 
foramen is situate in the centre of the parietal suture. “ The occipital outline of 
the skull is much less sinuous than in Archegosaurus and Trematosaurus, there being 
only a moderate transverse concavity on each side between the mastoid and 
mpanic lines, instead of a deep notch.” The occipital condyles are figured as 
close together. 
' “Breadth of the specimen in its present condition, 2} in. Breadth of occiput 
outline, about 2} in. Length of occipitals, 41 lines; breadth, 32 lines. Length of 
parietals, 81 lines; breadth anteriorly, 32 lines ; posteriorly, 3 lines.” 
The teeth figured artd described as possibly those of Dictyocephalus appear to be 
Deinosaurian, The rib and “bone of the forearm” have no Labyrinthodont cha- 
racters. The skull is doubtless that of a true Labyrinthodont, though we are unable 
to assign it a definite place in the order. 
D. evecans, Leidy. 
Locality. Coal-field (Triassic) of Chatham County, North Carolina. 
References. Emmons, American Geology, pt. vi. p. 58, figs. 31, 82 [1857].— 
Leidy, Proc. Acad. Nat. Sci. Philadelphia, vol. viii. p. 256 [1857] 
