Permian Productinae and Strophalosiinae of W.A. 
9 
As may be seen from the table the shells change from a lirate, concen- 
trically wrinkled form with a low linear area to an unwrinkled form with 
a high triangular area ornamented only by spines and growth lines. 
In India, the evidence of a parallel evolution of Aulosteges is not sa 
clear, but is indicated. Aulosteges medlicottianus occurs in the lowest fossili- 
ferous beds, the Amb, of the Salt Range, while Aulosteges (Strophalosiina)i 
tibeticuSj which has the same characters as Aulosteges magnicostatus (con- 
centric wrinkles with radial costae anteriorly) is found in the Middle Pro- 
ductus limestone. Aulosteges dalhousii from the Upper Productus Limestone 
has the same characteristics as Aulosteges guadalupensis. 
Among the Australian form a similar parallel can be traced. A series 
of forms appears connecting Aulosteges haracoodensis with T aeniothaerus 
sub quadrat us. The latter species has no concentric wrinkles, a low linear 
area and the spine bases on the anterior part of the shell sometimes elon- 
gated as radial ridges. Aulosteges haracoodensis is ornamented by spines 
and growth lines only, and has a higher triangular area. Both these end 
forms occur in the Fossil Clift Beds, Irwin River, although in the North-West 
Basin Aidosteges haracoodensis does not appear until much higher in the 
sequence. Judged by the rate of change of the American forms T aeniothaerus 
suhquadratus would appear in the equivalent of the Hess beds and Aulosteges 
haracoodensis not until the Word. The evolution of the forms may, how- 
ever, have taken place at different rates in the two areas. 
A second shred of evidence of the general stage of development of the 
Western Australian fauna is provided by the Dictyoclostus group. In that 
genus there is a marked tendency for the area of reticulate ornament to 
decrease as the species become younger. Thus in Dictyoclostus semireticidatus 
from the Lower Carboniferous of the British Isles the reticulation may be 
found over the whole shell though not as clearly marked anteriorly. In the 
Permian species, however, the reticulation is confined to the posterior part 
of the shell. D. spiralis, indicus, vishnu, aratus and stihcostatus is an ascend- 
ing stratigraphical series from the Salt Range (Waagen 1884) and shows 
a gradual decrease in the area of reticulation of the species in the order 
named. The Western Australian shells, Dictyoclostus callytharrensis, have 
the reticulation covering but a small area of the valve and possess a ginglymus 
while the ears are separate from the flanks. All these features are seen only 
among the younger members of the genus. 
IV. CLASSIFICATION. 
Family PRODUCTIDAE Gray, 1840. 
In his original description of the family. Gray included the genera 
Productus, Strophalosia, Chonetes, Leptaena, Orthis, Strophomena and 
Calceola. King (1846, p. 94) restricted the family to those shells “distin- 
guished by the form of the ovarian spaces and the presence of spines, and 
excluded the genera Strophomena, Orthis, Leptaena, Chonetes and Calceola, 
Gray (1848, p. 438) was opposed to this restriction and enlarged the family 
to its original content. Gray^s opinion, however, was not widely accepted, 
and King's diagnosis became the diagnosis of the family. 
