10 
Unto (?) 1Viaxa:\iattexsis, Elh.,jnr. 
PI. rr, Figs. 1-4. 
Unio IFiduamaltensis, Etlieridge ,jnr. (M.S.), in Wilkinson, “ Notes, Geology 
New South Wales,” second edition, 1887, p. 7G. 
Sp. Char . — Shell ovatc-obliqncly ohlong, laterally compressed, thin. 
Dorsal margin, or hinge line, straight posteriorly, angulatcd at the anterior 
end, but in its entire length not as long as the shell ; ligament small, and 
jirojeeting bnt little aliovcthe dorsal margin. Ventral margin nearly straight, 
with a slight sinns at the middle. Anterior end small, very much com- 
pressed, and with the margin rounded ; posterior end compressed, the margin 
ol)liqucly truncated. Umbones small, obtuse, and ill-defined, sometimes 
eroded; diagonal ridge well-marked, although not strong; the flanks of the 
valves decrease rapidly in convexity from this ridge to the ventral margin, 
but an almost impereej^tible sinus traverses them upwards from the ventral 
marginal inflection. Posterior slopes small, steep, and not concave. Internal 
characters of the cardinal margin unknown. Pallia! line not deeply 
impressed. Small, deep, muscular pits, more or less arranged in a semicircle, 
occupy the umbonal cavity ; anterior and posterior adductor impressions 
unknown. Sm-face with fine concentric ridges, subdivided l3y distant subim- 
bricating growth laminic, the whole covered with a very regular and beautifid 
microscopically and longitudinally wrinkled epidermis. 
Ohs. — Although the reference of tliis species to C'ulo is only jiro- 
visional, it yet recalls to mind many characteristic species of this genus in 
the general outline of its shell. 
The compressed valves, bent anterior cardinal margin, rounded diagoiral 
ridge, and sharp ends will at once serve to distinguish it from other species 
which may at any future time be met with at a similar horizon. The dis- 
jointed and delicate transverse wrinkling of the epidermis is a very important 
character in C . (?) IVianamattensis, and gives to the shell a peculiarly smooth 
and glossy appearance. It covers the whole of the valves from the umbone 
to the ventral margin, and it appears to me to be a truly epidermal character, 
and in no way connected with the shell structure. It must not in the least 
be mistaken for the irregular wrinkling, or rather crumpling, met with in 
many papyraceous-shelled mollusca of the Carboniferous rocks in otlicr parts 
of the world, such as seen in the genera Anlhracowya, NaiacUtes, and the 
like. 
