8 
K. L. Prendergast. 
completely obliterated the median depression. On its dorsal face, also, the 
process of this species is much reduced, faint depressions marking the posi- 
tions of the dorsal concavities. 
Where the median depression is present in the ventral aspect, as in 
Anlosteges and Prodnetus s.l. the depth of this depression is regulated to 
some extent by the inclination of the cardinal process to the plane of the 
brachial valve. Where the process is erect the depression is shallow but 
where it becomes sharply bent over, as in Anlosteges ivangenheimi, the sulcus 
is very deep. 
Marginal Eidgesy etc. — Marginal ridges are sometimes developed in 
species of this group, for example, Strophalosia kimberlegensis. These ridges 
are always low and not prominent. In some species of Aidosteges a pro- 
nounced ridge may be developed along the hinge-line, as in Anlosteges 
wangenheimi (see Fig. 4, p. 33). This ridge is placed anterior to the hinge- 
line. 
Pedicle valve . — The muscle impressions of the pedicle valve are of the 
same general form although they vary throughout the group. The adductors, 
dendritic in Atilosteges and Prodnetus s.l., non-dendritic in Strophalosia, are 
median and separated by a groove or a small ridge. The diductors are large, 
flabellate and longitudinally striate. In some species of Strophalosia the 
ears of the pedicle valve are thickened so that when the shell is closed the 
ears fit closely one upon the other. This thickening is seen as a flat ledge 
on the inside of the valve and projects slightly over the visceral cavity. 
For a description of the microscopic structure of the shell reference 
should be made to Muir-Wood (1928, p. 29) and Dunbar and Condra 
(1932, p. 179). 
TIL TRENDS IN THE PRODFCTINAE. 
Although sufficient data are not yet available for the recognition cf 
lineages, nevertheless some indication of possible trends can be given, based 
on the fauna of other areas, and these ideas can be applied to the Australian 
forms. 
The table below shows the distribution and characters of the species of 
Anlosteges from the Permian of the Glass Mountains, Texas (King, 1930). 
— 
Wolfcamp. 
Hess. 
Leonard. 
Word, 
Delaw’are 
Mtn, White 
Limestone of 
Guadalupe. 
A. wolfcampensis 
A. rnedlicottianus 
lb, 2b, 3b 
lb, 2b, 3b 
lb, 2b, 3b 
lb, 2b, 3b 
lb, 2b, 3b 
A. ynagnicostatus 
A. triagonalis 
A. subcostatus 
A. beedei 
A. guadalupensis 
A. tuherculatus 
lb, 2b, 3a 
la, 2b, 3a 
lb, 2b, 3a 
la, 2b, 3a 
la, 2a, 3b 
la, 2a, 3a 
lb, 2b, 3a 
la, 2b, 3a 
la, 2a, 3a 
la, 2a, 3a 
la, 2a, 3a 
Where 1. radial costae ; b, present, a, absent. 
2. concentric wrinkles ; b, present, a, absent. 
3. area ; b, low and linear, a, higher and triangular. 
