Permian Productinae and Strophalosiinae of W.A. 
7 
The variations within Productus s.l. are numerous. In the semiretieulate 
group as Muir-Wood (1928, p. 18) says; — 
Cardinal Process of Aulosteges barncoodensis Eth. fil. (X3). 
*‘The cardinal process projects beyond the margin of the brachial 
valve and is divided by a median furrow into two parts which are smooth 
and rounded ; these are continued dorsally as to two curved laminae, 
separated from the median septum by deep sulci. The dorsal view of 
the process show's it to be trilobate and transversely striated.” 
This condition can be readily understood by reference to Fionre 2 (p. 15) 
showing the cardinal process of Dictyoclostus callythorrensis n.sp. In this 
species as in all Dictyoclostids the whole cardinal process is flattened and 
widened and the lateral lobes have been rotated through nearly 90° until, 
instead of being parallel to the central lobe, they lie at right angles to it 
and parallel to the hinge-line. 
In Taeniothaerus, Linoproductus and Waagenoconcha the modification 
has taken quite a different form, as in these genera the tendency has been 
for the process to elongate and for the lateral lobes to be distinct and 
separated from the central lobe (see Taeniothaerus subquadratus (Morris), 
Figure 3, p. 28). The median depression of the ventral aspect is distinct 
and continues to the apex of the process but the posterior part of the process 
is now trifid even in its ventral aspect. In Taeniothaerus the process is still 
compact, but in Linoproductus (e.g. Linoproductus cora (d’Orb.) Kozlowski, 
P- 14) the lateral lobes have splayed out and the process appears; 
winged. In Waagenoconcha (e.g. Waagenoconcha humholdti (Waagen), 
Kozlowski, fig. 9, p. 15) the dissection of the lobes is continued further 
towards the hinge-line than in the other g'enera. In the aged specimens 
Kozlowski found that the median lobe sometimes divided giving what has 
been described as a quadrilobed cardinal process. 
The shells so far considered have had the median septum separated 
from the cardinal process by a sulcus of varying depth. In the Strophalosias, 
on the other hand, the median septum arises Avithin the cardinal process. The 
septum swells out betAveen the sockets and completely fills the median 
depression betAveen the ventral lobes. This sAvelling is showm in Strophalosia 
Umberleyensis n.sp. (Fig. 8, p. 48) in Avhich a part of the depression may 
be seen posterior to it. This outgrowth of the median septum would give 
additional support to the socket plates. The median septum in Strophalosia 
etheridgei n.sp. (Fig. 7, p. 44) is not unduly swollen, but has, nevertheless, 
