REPORT ON FOSSIL FISHES. 63 
safely assume the presence of one here also, symmetrical with that on the 
opposite aspect. 
As indicated above, I believe this fragment to be the hinder end of a fish 
with continous diphycercal dorso- and ano-caudal fin; but as the want of the 
head and abdominal parts render it difficult to distinguish with accuracy the 
symmetrical dorsal and ventral margins, and neural and hemal aspects, I 
have appended queries to these terms where it has been necessary to use them. 
The specimen from Glencartholm.—This specimen (PI. IV. fig. 6) is 23 inches in 
length, and presents us in the first place with a head, the length of which is } inch. 
Unfortunately, very little can be made out concerning the cranial structure. 
On the cranial roof two distinct frontal bones are observable, ganoid externally, 
and faintly sculptured with indented lines and punctures. A distinct opercular 
apparatus is seen consisting of broad plates; but owing to the crushing they 
have undergone, it is impossible to make out the number or shape of the 
individual elements. The suspensorium is not directed backwards as in typical 
Palzoniscide, but seems nearly vertical, if not indeed inclined slightly forwards. 
A considerable portion of a stoutish mandible is seen, marked externally with 
delicate longitudinal ridges, while above it is a portion of a maxilla, but no 
teeth are visible on either jaw. There is also an indication of the position of 
the orbit, right over the middle of the mouth. 
Behind the opercular bones, and somewhat overlapped by them, are some 
traces of a pretty strong clavicle. 
The body is almost completely covered up and obscured by an obstinately 
adherent thin layer of matrix, nevertheless, certain parts are seen, though 
faintly, as if through a veil. The body extends back for 22 inches, or six times 
the length of the head before it is cut off by the edge of the stone; and as it is 
clear that a pretty considerable portion of the caudal extremity is wanting, the 
fish must have presented a somewhat narrow and elongated contour. The 
points of structure here observable are mainly indications of the internal 
skeleton. For nearly an inch behind the head these are very obscure, consist- 
ing principally of an irregular line, with here and there little bits of bone 
shining through, which are probably portions of neural arches; behind 
this, however, the line of the vertebral axis is very apparent, although the 
associated structures are very much more clearly seen on the neural than on 
the heemal aspect. As in the specimen from Tarras Foot, there is no evidence 
of vertebral bodies, and the notochord may therefore be presumed to have 
been persistent. On the dorsal aspect of the axial line there is, as in the 
former specimen, a series of slender neural spines, inclined obliquely upwards 
and backwards ; they are pointed distally, but proximally they are enlarged 
VOL. XXX. PART I. K 
