180 
RECORDS OF THE AUSTRALIAN MUSEUM. 
should be sufficient to separate them. I have seen no trace of an 
external ligament in actual specimens of Stutchburia, but in one 
of Morris’ figures! of S. costata , as it must now be called, there is 
some shading above the hinge line that certainly does present the 
appearance of a cartilage, but T think it is misleading and not 
structural. 
Before proceeding with the specific descriptions, a few generic 
points may be dwelt on more in detail. The dorsal or cardinal 
margins, or hinge lines of the valves, are erect and unquestionably 
closed, but on their inner and lower sides form thickened obtusely 
rounded edges. These continue past thein conspicuous umbones, 
and in their substance immediately anterior to the latter, are 
excavated two depressions, one in each valve, which, in all prob- 
ability gave attachment to the ligament at this end of the shell. 
If not of this nature, the only other solution is that these depres- 
sions are muscular. In the cast these thickened internal margins 
are represented by wide, shallow, longitudinal concavities, whilst 
the depressions are indicated by two sharp projections about midway 
between the umbones and the anterior adductor scars. The latter 
are large and deep, in the type species at any rate, and must have 
received strong and well developed muscles. On their posterior 
sides the interiors of the valves were much thickened, and in con- 
sequence deep depressions are left on the surface of casts, circum- 
scribing the impressions of the muscles, which stand out boldly 
from the general surface, with an oblique inclination to the anterior 
The posterior adductor scars are situated high up on the flanks 
of the valves, immediately under the hinge lines, and although 
conspicuous, are less so than the anterior. They have an oblique 
inclination to the posterior, with the test correspondingly 
thickened on their anterior sides, but to a smaller extent than 
those of the other extremities of the shell, The simple pallial scars 
are well defined, continuous, and from their prominence in casts 
must have presented deep and sharp lines on the valve interiors. 
The following are the species known to me : 
Stutchburia costata, Morris , sp. 
(PL xxxi., fig. 1.) 
Orthonota ? costata, Morris, Strzelecki’s Phys. Descrip. N.S. Wales, 
&c., 1845, p. 273, pi. 11, f. 1 (l excl. f. 2). 
Cardinia ? costata , Dana, Wilkes’ II. S. Explor. Exped., x., 1849, 
p. 692 (? pi. 4, f. 8, Sa, 6, c.). 
Pleurophorus Morrisii, DeKoninck, Pal. Foss. Nouv.-Galles du 
Sud, 3, 1877, p. 143, pi. 20, f. 5. 
Pleurophorus Morrisii , Eth. fil., Cat. Austr. Foss., 1878, p. 77. 
f Strezelecki. — Phys. Descrip. N. S. Wales, &c., 1845, pi. 11, f. 1. 
