38 
J. R. RICHARDSON 
Measurements. (In mm.) 
Specimen 
Total 
length 
Dorsal 
valve 
length 
Breadth Depth 
NMV PI34228 
11.0 
9.0 
8.6 
5.6 
NMV P134231 
10.3 
8.9 
8.6 
5.6 
NMV P134232 
10.1 
8.7 
8.6 
5.4 
NMV PI34230 
10.7 
8.9 
8.2 
5.7 
NMV P134241 
9.3 
7.8 
7.4 
4.8 
NMV PI34242 
8.4 
7.6 
6.5 
3.9 
Description. Outline ovate; moderately bicon¬ 
vex. Anterior commissure slightly sulcate. Beak 
nearly straight, approximately one-fifth of valve 
length; symphytium slightly concave with 
median longitudinal ridge; cardinal margin 
gently curved. Hinge platform with wide, 
shallow hinge trough; anterior surface of car¬ 
dinal process slightly variable in size, not 
extending beyond posterior half of platform. 
Septum extending to mid-length of valve, high 
anteriorly. Loop with ascending and descending 
branches fused anteriorly. 
Elderra gen. nov. 
Name. From the Aboriginal (handsome). Gender 
feminine. 
Type species. Elderra toorlooensis sp. nov. from the 
Miocene of Australia. 
Diagnosis. Sulcate. Beak suberect, beak ridges 
sharp; symphytium with median and lateral 
ridges; cardinal margin curved. Hinge platform 
with hinge trough. Loop without septal connect¬ 
ing bands. 
Comments. Elderra contains only one species 
which is similar in many features to variants of 
species included in Magadinella , but which is 
notably less variable in size, shape, beak charac¬ 
ters, and in the extent of thickening of the car- 
dinalia. Essential distinguishing features are the 
loop stage and the ridges which demarcate the 
borders of the symphytium. 
Elderra toorlooensis sp. nov. 
Fig. 4A-F 
Limestone, Wuk Wuk Marl Member (Batesfordian- 
Bairnsdalian, Lower-Middle Miocene): lower beds 
Skinner’s; lower and upper beds, Drier’s. Gippsland 
Limestone, Bairnsdale Limestone Member (Baims- 
dalian, Middle Miocene): Pound Swamp; shaft on 
Rosehill Farm. Tambo River Formation (Mitchellian 
Upper Miocene): cliffs on left bank of Tambo River! 
Swan Reach; cutting near Toorloo Arm. Unknown 
Tertiary formation: oil shaft dump, Lakes Entrance. 
All material cited is housed in the Museum of Vic¬ 
toria. 
Measurements. (In mm.) 
Specimen Total Dorsal Breadth Depth 
length valve 
length 
NMV P17351 
NMV PI34217 
NMV PI34218 
NMV PI34219 
NMV PI34220 
33.1 
29.0 
25.9 
16.8 
29.8 
25.7 
22.7 
16.3 
31.1 
27.2 
22.6 
15.7 
19.8 
26.2 
22.5 
15.1 
29.5 
25.1 
21.0 
17.7 
Description. Outline ovate, biconvex. Anterior 
commissure gently sulcate. Symphytium slightly 
concave, with median ridge and lateral ridges at 
junctions of symphytium and palintropes. 
Hinge platform trapezoidal in outline; socket 
ridges projecting posteriorly beyond umbo as 
two pointed processes, fused anteriorly with 
swollen crural bases; hinge trough extending 
length of platform, deeper posteriorly; cardinal 
process with slightly bulbous anterior surface. 
Septum short, base thick, crest sharp. 
Comments. Little morphological variation is 
evident in specimens from the environs ofToor- 
loo Creek and the Tambo and Mitchell Rivers. 
The specimens collected from an oil shaft dump 
at Lakes Entrance are smaller in size and slightly 
narrower in outline with stronger curvature of 
the cardinal margin, features which alone do not 
justify taxonomic separation. 
Adnatida gen. nov. 
Name. From the Latin adnatus (united), in reference 
to the components of the cardinalia. Gender femi¬ 
nine. 
Type species. Magasella deformis Tate, 1880 from the 
Eocene of Australia. 
Name. From the type locality. 
Type material. Holotvpe NMV P17351 and paratypes 
NMV P17352, PI7353, P86845, PI34217-PI34220, 
from the Gippsland Limestone, Bairnsdale Limestone 
Member (Bairnsdalian, Middle Miocene), Toorloo 
Creek, Lakes Entrance, Victoria. 
Other horizons and localities. Victoria. Gippsland 
Other species. A. gnangarensis sp. nov. 
Diagnosis. Sulcate. Beak pointed, erect, foramen 
small; symphytium concave; beak ridges and 
cardinal margin curved. Hinge platform heavily 
thickened without hinge trough or pits, with pos¬ 
terior surface of cardinal process only identifi¬ 
able structure. 
