49 
The anterior ends in E. cordatum are comparatively small, nearly the 
whole of the valves being posterior to a line dropped from the umbonal 
apices. This species is, therefore, according to our view, very inequilateral, 
and not, as Morris stated, “ nearly equilateral.”^ This condition also obtains 
in E. hohartense. 
The anterior regions may be described as antero-ventrally protuljerant, 
the margin below the lunule fairly convex. 
In both Dana’s and Morris’ figures the anterior ends of tlie valves 
are always represented as more produced than the posterior,'^ and more 
compressed®; the marginal outline is also more elliptical than the posterior 
{E. eUiptica, Dana). 
The large posterior ends are highly inflated immediately behind and 
below the umbonal region, giving the valves their great ventricosity. The 
'broad convex surfaces rapidly pass into the steep })osterior slopes, hut these 
are not separated from the umbonal slopes by diagonal ridges; tliere is no 
marginal inflection, the dorso-posterior angles l)eing rounded off. There are 
no traces of posterior alations, though the valves are sometimes flattened in 
that region. The ventral and posterior margins form a wide, somewhat 
oblique curve. These characters are clearly seen in E. cordatum and less so 
in E. hohartense. 
It must be pointed out that a small posterior wing-like extension is to 
he seen in one of Dana’s figures of his E. elUptica^ •, hut this must he regarded 
as, at any rate, a very inconstant character. 
4. The umhones are prosogyrate, incurved, and with acute, small apices, 
always approximate, in some cases touching, hut usually slightly separated — 
in only one case have we seen them any appreciable distance apart (PI, 
XVIII., fig. 3). The umbonal regions are very pronounced, high, and 
prominent, especially in E. cordatum. 
Morris described the umhones of Eurydesma cordata as incurved, thick, 
and approximate®; Dana as approximate, incurved, and curving a little 
* Morris in Strzelecki — Phys. Descr. N. S. Wales, &c., 1845, p. 276. 
^ Morris in Strzelecki — Op. cil., PI. XII. ; Dana in Wilkes — Op. cit., PI. VII., fig. 6<', 
* Dana in Wilkes — Op. cit., PI. VII., fig. 6a. 
* Dana in Wilkes — Op. cit., PI. VII., fig. 6<i. 
®Morris in Strzelecki — Op. cit, p. 276. 
