50 
CH 1M.ZEK,0IDEI. 
above the right mandibular tooth rests the small incisor¬ 
like presymphysial tooth (ps.), which is shown in side view 
and transverse section, of three times the natural size, in 
figs. 4 a, 4 b. This tooth is much worn at its rounded 
functional extremity, and appears in transverse section 
(fig. 4 b) as if bent upon its mesial longitudinal line, which 
is in the form of a rounded ridge externally and a deep 
concavity internally; the tubular dentine does not cover 
the whole of the inner face, but forms a band occupying 
the greater part of the width of the concavity. The pair 
of anterior upper teeth (y.) is displayed from the oral 
aspect, each consisting of a broad triangular hinder portion, 
and a narrow quadrangular anterior portion, the latter 
crossed by few transverse ridges of laminated dentine. A 
fragment of one of the hinder upper teeth (pi.) is too 
imperfect for description. Some of the thorn-shaped der¬ 
mal tubercles, upon expanded bases, evidently from the 
rostral spine, occur higher upon the slab (t.) : and the 
basal half of the spine itself is shown from the dorsal 
aspect immediately adjoining. This spine expands at its 
base more' gradually than that of Squalorcija , which it 
otherwise resembles in form; and there are traces of a 
very fine superficial granular ornament. Enniskillen Coll. 
P. 1158. Fragmentary remains of head and dorsal fin-spine. Por¬ 
tions of the hinder pair of upper teeth are shown from the 
attached surface, and further posteriorly there is a trian¬ 
gular dermal plate, exposed from the outer aspect. This 
plate is raised to a somewhat excentric acuminate apex, 
and is covered with tuberculations arranged more or less 
in radiating lines ; it is shown, of twice the natural size, 
in PI. III. fig. 4. The dorsal spine is much crushed and 
abraded, but exhibits a few downwardly pointing posterior 
denticles distally, while a long series of upwardly directed 
denticles is preserved on the anterior border. Egerton Coll. 
P/ 3099. Left mandibular tooth, exposed from the oral aspect, and 
shown, of the natural size, in PI. III. fig. 3. The sym¬ 
physis (fig. 3, a) is narrow and shows the characteristic 
bevelling (s), much extended, probably for the accommo¬ 
dation of the median incisor-like tooth; while the oral 
surface is undulating, with one oblique median ridge and 
a somewhat raised post-oral border, neither parallel with 
the symphysial border, but much less nearly vertical. The 
