13 
presented witli the features seen in PI. 11, fig. 12. Posterior to the umhones 
it Avill 1)0 observed the liingo is perfeetly straight ; hut in front of them there 
is a constant flexure, or double flexure, Avhich seem to indicate the presence 
of cardinal teeth. 1 cannot, however, account for this appearance in any 
other way. 
In Utiio tlie anterior cardinal teeth are 1 — 2, or 2 — 2 ; hut in some 
robust species the 1 — 2 arrangement appears to become reduced to 1 — 1. In 
such instances there is probably little difference between a dental formula of 
this nature and the structure observed in the Powral shells. 
The eroded state of the umhones is very marked in both the typical 
species, so much so in some individuals as to almost expose the interior cavity 
of the shell, and render the uml)onal muscular scars outwardly perceptible. 
Tifpe . — JJaionella Boicralensls, sp, noo. 
UnIONELLA BoWIIALENSIS, Sp. HOC. 
PL I, Figs. 21-2.3 ; PL II, Figs. 8-14. 
Sj). Chav. — Shell short, somewhat nasute, moderately convex, com- 
pressed and rather sharply produced posteriorly. Cardinal margin to some 
extent arched, ligament small, short ; ventral margin slightly convex. 
Anterior end shorter and much more gibbous than the posterior; margin 
rounded. Posterior end small, obtusely pointed ; margin rounded, obliquely 
so above. Umhonal region and body of the shell gibbous, and rapidly 
declining to the ventral margin. Umhones depressed and inconspicuous, at 
times much eroded ; diagonal ridge rounded, inconspicuous; posterior slope 
hardly differentiated from the general body of the shell. Anterior adductor 
impressions deep ; umhonal scars extending in a line from the anterior 
adductor into the umhonal cavity, and there clustered. Ornament of fine 
concentric lines, with distant lamime of growth. 
Ohs. — This, the most abundant form at Bowral, is distinguished from 
the succeeding species by its much shorter and nasute outline. The cardinal 
margin is shorter, and the upper part of the posterior margin more ol)liquely 
directed. The flanks of the shell also appear to he more evenly rounded. 
Localitp. — Piailway Cutting, near Gibraltar Tunnel, Bowral, Co, 
Camden. 
Ironstone hands in the AUianamatta Shale. 
Colleciov. — Mr. B. Bunstan, 
