M ordacia ■ — Str ah an 
417 
Fig. 1. A, Macrophthalmia stage; B, Ammocoete of Mordacia mordax. 
a jar of ammocoetes labelled, "Geotria, 1925, 
from Sydney, N.S.W.” For want of better knowl- 
edge, this diagnosis might have been accepted, 
had the jar not also contained a macrophthalmia 
(a large-eyed, recently-metamorphosed stage) 
which was markedly different from the macroph- 
thalmia of G. australis. It possessed two tri- 
cuspid supraoral laminae which showed it to be 
a Mordacia, and three conical teeth anterior to 
the supraoral lamina and separating the rows of 
lateral tooth plates, which identified it as M. 
mordax. This stage in the life history of the 
species has not previously been recorded or 
described. 
The specimen, which is preserved in alcohol, 
is of a uniformly pale yellowish-brown colour, 
as are the ammocoetes with it. The body is 
laterally compressed, much more so than in an 
ammocoete of the same length. It is 122 mm. 
long, being about 2 cm. shorter than the largest 
ammocoete in the sample. The eye is large and 
prominent and the iris has a silvery sheen. Meas- 
uring from the anterior tip of the head, the 
nasal aperture lies at 6 mm. and the centre of 
the eye at 7 mm. Eight lateral line pits form 
an infraorbital series and no other lateral line 
organs are discernible. The branchial region ex- 
tends from 12 mm. to 22 mm. The first dorsal fin 
arises at 70 mm. and extends to 76.5 mm.; the 
second dorsal fin extends from 88 mm. to 108.5 
mm. and is contiguous with the caudal fin. All 
the fins have distinct fin rays and are rather 
triangular in profile, differing from the fins of 
the ammocoete, which take the form of a low 
quadrilateral. The anterior border of the cloacal 
aperture lies 102 mm. from the anterior end 
of the body (Fig. 1 A). 
The mouth aperture is oval in shape, being 
longer longitudinally than transversely (Fig. 2). 
When opened to its full extent, its diameter is 
less than the diameter of the body. The mouth 
is surrounded, except posteriorly, by small, 
bluntly conical cirri lying just outside the rim 
of the buccal funnel. Just within the rim is a 
complete series of small, flat, fringed processes 
lying closely side by side. Two large supraoral 
tooth plates lie just anterior to the centre of the 
buccal funnel, separated from each other by a 
distance equal to the width of a tooth plate. Each 
tooth plate bears three sharp-pointed cusps 
which are directed posteriorly. From the shape 
of the tooth plates, it appears that each tricuspid 
plate may have arisen by the fusion of three 
unicuspid elements. Anterior to the supraoral 
tooth plates and in the mid-line are three small 
unicuspid teeth arranged in a triangle with the 
apex pointing anteriorly. On the right and on 
the left side of the buccal cavity is a series of 
five small bicuspid lateral tooth plates arranged 
radially. Posteriorly, external to the infraoral 
lamina, is a series of eight bicuspid tooth plates, 
also having a radial orientation. The infraoral 
lamina bears nine low, pointed cusps, the penul- 
timate of these at each end being slightly higher 
than the others. The anterior lingual tooth plate 
has a finely serrated edge. The two posterior 
lingual tooth plates cannot be seen very well in 
the specimen. 
COMPARISON OF MACROPHTHALMIA STAGES 
OF G. australis AND M. mordax 
The macrophthalmia of G. australis has been 
described by Maskell (1929) and it is unneces- 
sary to repeat the description here. Table 1 
summarizes the differences between the ma- 
crophthalmia stages of the two species. 
Apart from the dentition, which alone is suf- 
ficient to separate the macrophthalmia stages of 
