273 
Ols. The present shell appears to correspond in general ontline with those 
American Bivalres for wdiich Prof. James Hall and Mr. Whitfield have proposed the 
above genus. There is, however, a less arcuate outline, and a more determinate diagonal 
ridge. The concavity above the latter is a very marked feature in this species. Purther- 
more, I have not seen “ the single strong wedge-form tooth in the left valve, and 
corresponding cavity in the right,” which appears to distinguish Modiomorplia . 
One specimen seems to show indications of some radiating ribs on the body of 
the shell, parallel to the diagonal ridges, but they are very indistinctly preserved. 
Loc. and Horizon. Hawkins’ Gully, Kroombit Diggings, Port Curtis {W. H. 
Rands) — Gympie Beds. 
Modiomoupica mytiiipoemis, sp. nov., PI. 14, fig. 5 ; PL 40, fig. 4. 
Sp. Char. Shell transversely ovate, modioliform, convex, curved, moderately 
gibbous, expanding posteriorly, dorsal and ventral margins divergent. Anterior end 
small but non-lobate, its margin rounded. Posterior end expanded, gradually com- 
pressed, the convexly rounded margin gradually passing imperceptibly into the dorsal 
margin, the widest portion of the curve being above; ventral margin concave cen- 
trally, convex anteriorly and posteriorly ; cardinal or dorsal margin elevated, nearly 
straight but not in the least angulated ; hinge-line of the left valve with a long socket 
Under the beaks for the reception of tooth of the opposite valve, and a long posterior 
lateral tooth; valves convex modianally, a broad and rounded diagonal ridge jiroceeding 
from the beaks and becoming lost towards the posterior end. Umbones small and quite 
interior, an almost imperceptible sinus running from them in each valve, to the ventral 
margins. Surface with broad concentric folds. 
Ohs. This shell is very lilco the smaller figure of McCoy’s Modiola crassissima,* * * § 
fiut not the larger one, and may even be the latter. But in the present shell there is 
Uo angulation of the posterior hinge-line, this and the posterior margin insensibly 
passihg into one another. Again, there is little or no sulcus from the umbones towards 
the ventral margin, the sinuation of the latter being much more gradual in the present 
shell, and placed nearer the centre of the margin, with a corresponding decrease in 
height of the posterior end. To some extent M. mytiliformis resembles Cypricardia 
^'m.hricata, Dana,t but in the figure of the latter the ventral margin is not at all inflected, 
^ud there does not appear to be any umbonal slope. Purthennore, the posterior end, 
judging by the surface ornament, was sigmoidal. In. PI. 38, figs. 12 and 13, is probably 
Represented the younger condition of this species, which is equally like Dana’s 
Cypricardia pr(srupta,X but the cardinal margin of the latter is too horizontal ; 
and again there is an entire absence of the diagonal convexity visible in our little 
shell. 
The young form (PI. 38, figs. 12 and 13) again might at times be mistaken for 
-L'aua’s Cypricardia simplex,^ but the same points will serve to separate the two. The 
Uame Cypricardia is merely quoted from Dana, as it is most inappropriate to these 
shells. 
Loc. and Horizon. Banana Creek, Banana, Dawson Eiver (R. L. Jack and C. TV. 
e Vis) ; Richards’ Homestead, three miles south-west of Mount Britton Towmship 
{R. Hull ) — Middle or Marine Series, Bowen River Coal Field. 
* Ann. and Mag. Nat. Hist., 1847, xx., p. 300, t. 15, f. 2 and 3. 
+ Geology Wilkes’ XT. S. Explor. Exped., Vol. x.. Atlas, t. 8, f. 5. 
t Hrid., i. 10. 
§ Ibid., t. 9, f. 2. 
