from the Shales of the Northumberland Coal-field. 367 
quarters of an inch wide, and, including the pedicle to which 
it is attached, it is one inch and three-quarters long; the 
under lobe is not much produced, and the upper is rather 
obtuse; no rays are perceptible. The scales are well pre- 
served, and are in an undisturbed state. Some of them are 
brilliantly glossy, and have towards the posterior angle a boss- 
like swelling ; others are dull and minutely granular. Which 
is the true natural surface it is difficult to say, though it seems 
probable that the latter is. Be this as it may, both kinds of 
seales are found scattered in the vicinity of the head and 
spine. 
: Acanthodopsis Egertoni, n. sp. 
A crushed head with the pectoral spines attached, a de- 
tached jaw or two, a few separate spines, and some scattered 
scales are all the remains that have occurred of the large 
species alluded to. The head, which could not have been less 
an two and one-quarter inches long, has one of the man- 
dibular rami well displayed, with the teeth attached; but they 
are, unfortunately, in a very imperfect state. The ramus is 
very similar in character to that of A. Wardi; but the den- 
tigerous bone does not appear to be striated; the styliform 
process is not much arcuated at the proximal extremity, and 
tapers gradually to the anterior point. The teeth are arranged 
in the same manner.as in the smaller species—that is, with the 
larger in the centre and smaller at the extremities of the jaw; 
with the aid of a detached mandible we are able to ascertain 
that there are seven or eight in each ramus; they are not 
nearly so wide at the base as in the previous species, and they 
are more regularly and finely striated. Some of the bones of 
the head are finely and regularly tuberculated ; these are pro- 
bably the orbital plates. The similar plates of the other 
species appear to be irregularly granular. 
_ The spines attached to the head are upwards of two and a 
half inches long, though they are not entire; but the largest 
detached specimen in our possession is quite an inch longer, 
though in it, too, the point is broken. This must have been 
longer than the largest mentioned by Sir P. Egerton; it is 
upwards of one-quarter of an inch broad, and is flat and 
curved like the others, resembling the blade of a scimitar; 
towards the base the inner margin is thickened and angulated, 
and a — line or groove extends from end to end a little 
within the anterior or arched margin; a few fine longitudinal 
lines are seen near to and almost parallel with the opposite 
margin; the pom appears to be rounded, but is not quite per- 
fect m any of our specimens. 
The scales which are found associated with the head and 
