MANSFIELD DISTRICT, VICTORIA. 
distal ends do not appear to have extended further back than the 
tips of the pectoral spines. Ridged ornament of both paired 
spines tuberculated ; the number of ridges cut by a cross-section 
of a full-grown pectoral fin-spine just behind its base of insertion 
about 13 to 15 on each face. 
General Form .- — The specimens of the head and abdominal 
region of this species are always exposed either from above or 
below, and prove that the greater part of the body was originally 
rounded or depressed in transverse section. The only known 
example of the hinder part of the caudal region (PI. Y, fig. 1) is 
displayed in side-view, and indicates that this part was more 
laterally compressed. The type-specimen seems to show the 
complete extent and shape of the head and branchial region, 
while this and another imperfect fossil (PI. I, fig. 7), with the 
caudal region just mentioned, appear to justify the specific 
diagnosis, which is illustrated by the accompanying restored 
sketch (text-fig. 1). 
Head . — So far as preserved in the type-specimen, the head 
exhibits nothing but the usual close armour of dermal tubercles, 
without any traces of teeth or circumorbital plates. It also lacks 
indications of branchial arches. The cartilage of the endoskeleton 
cannot have been sufficiently well calcified. for preservation. 
Fectoral Fin-spine . — The paired fins are represented in the 
fossils solely by their anterior spines, which are always imperfect 
and often preserved only in the form of natural moulds or 
impressions. Owing to its vertically-compressed shape the 
pectoral fin-spine is invariably exposed either from above or 
below, and it is shown on both sides of the type-specimen, of 
which the left portion is seen in PI. I, fig. 1 (c). Parts of this 
spine are also seen on both sides of the fossil in PI. I, fig. 7 ( b ), 
PI. II, fig. 2 (6), and PI. Ill, fig. 1. More satisfactory ex- 
amples for description are drawn in PI. II, fig. 1 (t?) and PI. IV. 
As indicated by the two specimens last mentioned, the base of 
insertion is much extended, its extent being probably greater 
than one-third of the total length of the spine; but this base is 
not very deep, and it appears to have been only quite slightly 
produced forwards in front of the exserted and ornamented 
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