Tertiary. | PALAZONTOLOGY OF VICTORIA. [Mollusca, 
Prats XLIV., Fira. 1. 
CARDIUM PSEUDOMAGNUM (McCoy). 
[Genus CARDIUM (Lin.). (Sub-kingd. Mollusca. Class Lamellibranchiata, Order 
Ishedrolotila, Fam. Cardiade.) 
Gen. Char.—Shell sub-cordate ; margins close or gaping anteriorly and posteriorly ; car- 
dinal teeth, 2, 1, or absent ; lateral teeth, one anterior and one posterior, or absent. Marine. 
Range in time from Palzozoic to Recent. 
The surface is usually costate, radiatingly, but in the section Protocardium the radiating 
ridges are only distinct on the posterior slope, and there is a slight sinus in the pallial scar. ] 
Descriprion.—Rotundato-quadrate, ventral margin slightly convex, nearly 
straight, inclined at about 80° to the nearly straight posterior margin, the respiratory 
angle between them being obtusely rounded; anterior margin broadly rounded, 
gradually arching into the ventral margin; beaks tumid, moderately oblique, sub- 
central, apical angle 79° in young, 80° in old specimens ; valves moderately tumid, 
greatest depth at about half the length from the beak, the marginal half more 
flattened than the rostral half, which is stronzly arched; posterior slope flattened, 
the diagonal bounding ridge broadly rounded. Ribs 50, sub-equal, flat, smooth, 
without spines or marked striz, and separated by very narrow sulci; their ends 
strongly toothing the internal margin. Length (of large specimen) from anterior 
to posterior margin, 84 inches; proportional depth from beak to ventral margin 
(perpendicular to latter), =° ; greatest depth of one valve, 74°. 
There is no Cardium in the Australian seas in the slightest 
degree resembling this fine species ; which is not very near any of 
the Tertiary species known to me in any part of the world. The 
nearest analogue I know of is the recent Cardium magnum 
(Born.) of the Gulf of Mexico, with which it agrees in size and 
approximately in shape and ribbing ; the posterior slope is larger, 
less oblique or more nearly rectangular in the fossil ; the ribs 
are also more numerous (about 33 in living species), flatter, and 
separated by much finer or narrower sulci. __ 
Very abundant in the Miocene Tertiary sandy beds (A‘ 22 and 
23), Bird Rock Bluff, near Geelong. 
EXPLANATION OF FIGURES. 
Plate XLIV.—Fig. 1, inner view of average specimen, natural size, showing the cardinal 
and lateral teeth and denticulation of the margin. Fig. la, profile view of same specimen. 
Fig. 1b, external view of same specimen, showing in the lower part the narrow sulci between the 
broad flat ridges when the surface is perfect, and showing in the middle and upper portion the 
narrower ridges and wider interspaces when the superficial layer of shell is removed. Fig. le, 
portion of surface magnified, showing the appearance of the ridges when the surface is perfect 
and removed, and their relation to the toothing of the margin. 
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