472 
margin long, nearly straight; ventral margin rounded at either end, almost straight 
along the centre. Anterior end nearly equal to the posterior, the roundly truncate 
margin obliquely curved upward.s, giving to the shell the described obliquity, the 
posterior only difEerentiated by its greater length. Umbones nearly central. Dorsal or 
hinge margin thickened with an antei’ior cardinal tooth, large, solid, and somewhat 
triangular, posterior cardinal tooth but little developed. Concentric lines of growth 
very regularly follow the outline, turning sharply towards the umbones on the anterior 
slopes, and curving rather obliquely up on the posterior end, but the shell is in reality 
nearly smooth. 
Ohs. This shell has given more trouble in its determination than any other in 
the whole Collection, and is referred to the present genus with great doubt ; it is probably 
the type of an undescribed genus. In PI. 27, fig. 4, the anterior end has been broken 
away, and on that account much of the anterior obliquity is lost, but this is apparent in 
PI. 28, fig. 2, which, I believe, is only the internal cast of Corhioella maranoana. This 
peculiar obliquity towards the posterior recalls the genus Qercomya to some extent, but 
there is an entire absence of the strong diagonal ridge and posterior slope of that genus. 
The upturning of the posterior dorsal margin arises from a peculiarity of the cast, and 
is perhaps structural, tieing probably the edge of the interior of the valves below the 
thickened hinge plate. It may, perhaps, be doubted if PI. 28, f. 2 and 3, are the 
internal cast of PI. 27, fig. 4, but there is a depression beneath the beaks in an example 
of the former answering to that visible in PI. 27, fig. 5, and, as already explained, the 
anterior end of PI. 27, fig. 4, is a good deal broken away. This species exists in Prof. 
Tate’s Collection from South Australia, and is termed by him Poromya, but it does not 
coincide with the original type of that genus. Prof. Tate’s specimens aud others from 
the cabinet of Mr. G. Sweet will eventually be figured. 
After considerable hesitation I pi’ovisionally refer this peculiar shell to 
Lycett’s genus Corbicella, from the fact that the structure of the hinge seems to agree 
better with that of the latter than with any other genus. The shell may readily be 
known by its ovoid, lengthened, smooth form. In these particulars, more especially 
the two last, it has considerable resemblance to some Oolitic species of Corbicella, but in 
the case of a shell like the present, in which the hinge is only partially preserved, it is 
necessary to speak with caution. 
hoc. Maranoa Eiver, half a mile above Mitchell Eailway Station, in a core of 
limestone (i2, L. Jack ; Q. Sweet — Colin. Sweet, Melbourne). 
Genus— UmCABBIUM, D'Orbigny, 1850. 
(Prod. Pal. Strat., i., p. 218.) 
UniCAEDirM Meeki, sp. nov. 
PI, 27, figs. 2 and 3 ; ? PI. 26, figs. 13-15. 
Sp. Char. Shell gibbous, ovate-trigonal ; cardinal margin angular ; umbones 
obtuse, a little elevated, with the beaks close aud approximate. Anterior side rounded, 
somewhat produced ; posterior end produced, becoming rather pointed at the posterior 
ventral angle ; posterior slope fiattened ; ventral margin forming a broad semi-oval 
curve. Anterior muscular scar narrow-ovate, pointed above, with its posterior margin 
elevated and ridge-like. Pallial line indistinct ; surface marked with fine lines o 
growth, which appear to widen out into flatter ridges on the body of the shell. 
,f 
