414 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
and his premature death finally prevented all chance of the work being completed 
by his master mind and hand :— 
Cochliodus contortus = Cochliodus contortus. 
C. magnus = Psephodus magnus. 
C. oblongus = Streblodus oblongus. 
C. acutus = Deltoptychius acutus. 
C. striatus = Xystrodus striatus. 
Peecilodus angustus = X. angustus. 
P. jones fcuaaea Fe 
Pp. Lan oral Peecilodus jonesil. 
P. obliquus = P. obliquus. 
P. subleevis 
P. parallelus | = Deltodus subleevis. 
With the addition of other species, the arrangement in the second column will 
be adhered to in the following pages. 
In 1867, Prof. Owen published a paper in the “Geological Magazine” (Vol. IV., p. 
59) on the mandible and mandibular teeth of Cochliodonts, in which he considers 
“that the extinct crushing sharks of the Mountain Limestone period, though 
instructively represented by a lingering member of a once numerous section of 
Chondropteri, must be relegated to a distinct though conterminous family, for which 
I proposed the name of Cochliodontidee, from what may be regarded as the repre- 
sentative genus, Cochliodus, Ag.” Specimens of the mandibles and teeth of 
Cochliodus contortus, Ag., (including Tomodus convexus, as described by Owen) and 
Streblodus oblongus, Ag., are described, with the result that Prof. Owen considers 
that the relative positions of the teeth of each ramus of the jaw with its symphysis 
corresponds with the parts of the mandibular rami of Cestracion containing the 
anterior crushing teeth, and that they afford no ground for assuming that the sym- 
physis was prolonged, as in Cestracion, for the support of conical or any other 
teeth. The mandible increases in depth posteriorly but diminishes in breadth, indi- 
cating a shape of jaw like that in Cestracion. ‘The structure of the bone resembles 
that of the better ossified parts of the chondrine of plagiostomous fishes. In another 
example in the Woodwardian Museum, Cambridge, the reverse of the above is seen, 
in which the posterior end of the right ramus of the mandible is of little breadth 
and depth, but it gains in both, and chiefly in the latter dimension, as it approaches 
the symphysis, and there rapidly acquires great breadth and thickness. From the 
oppositeness of these descriptions it may be inferred that the soft cartilaginous sup- 
ports of the teeth, during fossilization have been more or less subjected to pressure 
or other circumstances which have modified the form of the jaw, but at the same 
time the important fact is deduced that the teeth of Cochliodonts consisted of teeth 
whose convolutions were attached to, and partially embedded in a thick cartilaginous 
