Permian Productinae and Strophalosiinae of W.A. 
45 
bulbous top. This is, however, usually worn down so that the process appears 
to continue posteriorly at an even width. The semi-circular visceral portion 
■of the brachial valve is interrupted by the short median septum, which is 
.swollen between the rounded muscle impressions. The valve is hollowed out 
l)elow the sockets and in a direction parallel to the hinge-line, a ridge sei>arat- 
ing this hollow from the cardinal margin. 
Compariso7i with other species. — The small size of these specimens dis- 
tinguishes them from any species of Strophalosia so far described from West- 
ern Australia. They were labelled by Miss Hosking in the Geological Survey 
■Collection, as being young specimens of a new species. The geniculated 
margin of the brachial valve indicates, however, that they are probably in 
the adult or nearing the adult condition unless they are the young forms of a 
Prohoscidella-V[kQ Strophalosia. In the absence of any shells which might 
be assigned to such subgenus I have described them as adult forms. 
Many features of these shells are also common to Strophalosia clarkei 
Eth. til. and Strophalosia gerardi King, although they cannot be regarded 
as closely related to either of those species. The brachial valve particularly, 
with its silky lamellar structure, short hinge-line and rounded alar angles, 
resembles S. clarkei. The pedicle valve, however, would distinguish them at 
once from that species in its ornamentation showing a marked resemblance 
to S. gerardi; from young members of this species they would be distinguished 
by the shape and convexity of the pedicle valve. 
Strophalosia gerardi King. 
PI. V, fig?. 13, 16, 17. 
1846. — Strophalosia grrardi King, p. 93 footnote. 
, 1847. — Strophalosia gerardi King, de Koninck, p. 137. 
ISoO. — Strophalosia gerardi King, p. 96, pi. xix, figs. 6-7. 
1857. — Strophalosia gerardi King, Davidson, Introduction, pi. viii, fig. 211. 
1880. — Sirophaloeiia gerardi King, Etheridge, jun., p. 294, pi. xii, figs. 34-37; 
■pi. xiii, fig. 38. 
1884. — Strophalosia gerardi King, Etheridge, jun., p. 87. 
1892. — Strophalosia gerardi King, Etheridge & -Tack, p. 260, pi. xiii, fig. 18; 
pi. xiv, fig. 18; pi. xl, figs. 7-8. 
1932 . — StrophalosUi gerardi King, Eeed, p. 20, pi. i, fig. 7. 
Maferial.^ — Rolofype. Univ. Coll. Galway, I.F.8., Xo. E.C.D. 267. 
Diagnosis. — Shell outline transversely oval. Pedicle valve convex, non- 
sinuate; brachial valve concave following outline of pedicle valve. Ornamen- 
tation of concentric lamellae and adherent tapering sjjines. Area on both 
valves with pseudo-deltidiiim and pseudo-chilidium. Length of hinge-line 
less than maximum width of shell. 
Pedicle valve swollen, with greatest convexity in visceral region, non- 
geniculate. Cardinal angles obtuse, ears small. 
Bi'achial valve concave, greatest concavity near umbo, shell sloping 
thence gradually to all margins. 
Internal features unknown. 
Description of specimen. — Univ. Coll. Galway, E.C.D. Xo. 267. Viewed 
from the brachial side the shell is a regular oval in outline, the transverse axis 
passing postero-anteriorly. From the pedicle side it has rather a triangular 
aspect. 
