4 
convex and the edges thicker as they recede, producing an obvious 
contrast with the opposite conditions in the recent Chelymys. The 
first vertebral shield is narrower in proportion to its length, its hinder 
edge is straighter, and its form different in other respects. The 
surface pattern beneath the marginal shields is much as in C. macquaria, 
a plexus of fine branching and interosculating lines, but beneath the 
costal and vertebral shields the longitudinal markings are delicate 
raised lines or fine striae, frequently imperceptible in certain lights, 
but almost always sufficiently in evidence for determinative purposes. 
The centre of the space beneath the first vertebral shield is convex, 
but from this convexity caudad the surface subsides into a broad 
shallow depression, The rest of the plates entering into the composi- 
tion of the carapace as restored being shown in position on Plate 1, it 
is unnecessary to describe them separately. Assuming the figure to 
be moderately true to nature, the carapace in this species had the 
form of a short oblong, a little contracted anteriorly, with lateral 
margins which are broad, convex, and nonrevolute as far as the ninth 
peripheral, then increasing slowly in breadth and becoming a little 
concave on the upper surface as far as the uropygial plate which is 
gently convex in the centre. The arch of the carapace seems to have 
been moderately elevated; its crown a little depressed in the course of 
the vertebral line. The constituent species of the plastron (Plate II.) 
have been recognised by the similarity of their surface markings with 
those of the peripheral plates of the carapace, and the identification 
has been confirmed by the fact that the fragments of the two present 
themselves in a similar numerical superiority over all others. The 
average size of the species at maturity was, in linear measurement, 
about twice that of C. macquaria. Log. : Darling Downs, passim. 
CHELYMYS ANTIQUA, n.s.— A species of so infrequent 
occurrence that it is represented by four fragments only, a lophial 
and first pleural from young individuals, a first and one of the hinder 
pleurals from older carapaces. The hinder half of the lophial (Plate 
III., Fig. A) is strongly elevated, its lateral angles depressed. The 
nuchal shield is oblong, with diameters 8 : 6*5 ; it is much shorter than 
the adjacent marginals, yet protrudes a little beyond them, conse- 
quently the front edge of the first vertebral in contact with it is thrust 
forward between the first marginals to a much greater extent than in 
the recent species. The anterior edge of the first marginal slopes 
caudad, not, as in C. macquaria, cephalad. The convex portion of 
the plate is rather obscurely ribbed with longitudinal raised lines, the 
remainder of it bears only a few very irregular and almost obsolete 
ridges. The first pleural plate (Plate III., Fig. B) shows on its 
surface the groove between the first vertebral and first costal shields 
and parts of those bounding the second marginal and second 
vertebral ; the first of these shows that the first vertebral shield 
in this species had a straight lateral edge and a sharp posterior 
angle, and that the angularity of the edge of the second marginal 
was much greater than in C. macquaria. The surface markings on 
this plate differ from those of the living species only in being more 
delicate. A portion of a similar plate from an apparently mature 
individual (Plate III., Fig. C) has the same straight groove as the 
preceding and superficial lineations no coarser than in it. An 
abraded fragment from the upper (vertebral shield) end of one of the 
