259 
the vascular system. The shell has a silky a2)pearauee, and when weathered or decorti- 
cated, the shell-.substance is marked by a series of fine, wavy, vertical lines. The valve 
IS externally ornamented with a number of close, concentric, scaly laminas and a few 
scattered splines similar to the ventral. A series of spines are ako placed along the 
hinge of the ventral valve, erect, and gi'aduating outwards from the umbo. 
Obs. The history of Slrophalosia Clarkei is a brief one. It was originally 
described by Mr. Etheridge as a Productus, from indifferent material in the Daintreo 
Collection, and the external characters defined. Subsequently Prof. De Koninck placed 
under this name a shell in the AY. B. Clarke Collection, and described it in his Jlew 
South Wales Work. In my “Catalogue” I follow both these Authors in placing the 
species under the genus Productm, but had not then enjoyed an opportunity of examin- 
ing specimens. 
This interesting species, at the time my former description was written,* * was 
known under two conditions only — internal casts of the ventral valve, and dorsal valves 
retainiTig more or less of their shelly matter. More receirtly I have enjoyed the 
opportunity of examining no less than thirty-three excellently preserved specimens in 
the Mining and Greological Museum, Sydney, from IVew South Wales localities, several 
of which have the valves united. Nothing is brought more prominently forward by 
these specimens than the flatness and non-spinous condition of the dorsal valve, and 
herein, it appears to me, we have, in conjunction with the comparative absence of spines 
from the ventral valve, excellent specific characters for the separation of S. Clarkei from 
sillied forms. 
If we examine casts of the ventral valve, and compare them with the fine i7iterior 
of S. Ooldfussi, Munster, figured by the late Dr. Davidson,! it will be observed that in 
fig. 9, representing a east in a similar state of preservation to our specimens, there is, 
ns in the latter, the corresponding^blunt and gradually attenuated but prominent beak 
(figs. 29 aad30,*,i),J and deep pits left by the teeth of the ventral valve (fig. 30,«). Again, 
compare, in fig. 10 of the “Permian Monograph,” the concave or grooved back of the 
Umbo with that of the Queensland cast (figs. 27-30,i). Thirdly, the position of the 
ndductor scars in the same Permian figure is quite comparable with that of the Australian 
specimens (figs. 26-30, c,c,c,c). In Mr. Davidson’s figure, the deep pit or fossa in front of 
these impressions is not so marked as in our fig. 29 ; but this is itself a variable point 
lu the Australian shells. With regard to the cardinal muscular sears, we observe a 
perfectly similar arrangement — the p^osition identically the same, similar ridging and 
grooving, the only apjparent difference being that in the Permian S. Gold/iissl the 
abrupt or scarp-like side appears to bo towards the front, whereas in S. Clarkei it is 
towards the umbo or the hinge-line (figs. 27 and 29,e,e,c,(?). It must, however, not be 
orgotten that all these characters are open to much variation in development, but not 
’u feature, being very pronounced in some individuals, and feeble in others. 
It is strange that, out of the large series obtained by my Colleague from the Bowen 
Jtiver Coal Eield, so few specimens should retain traces of the septum, reniform impres- 
®ions, and other anatomical details. The usual condition under which the dorsal valves 
° 'S'. Clarkei arc presented to us is shown by figs. 18a, 19, and 20, a flat, bevel-edged, 
Juore Or less oval, silky shell, and, although viewed from the interior in each case, no 
race of the marked characters of figs. 21 and 23 are visible, but on the contrary 
iu the place of the strong cardinal boss and sejjtum, an oval gaji in the shell 
* Proo. B. Phys. Sou. Ediub., 1880, v., p. 289. 
t Mon. Brit. Permian Brach., t. 3, figs. 9-10. 
p, I These numbers and letters refer to the figures given in my former description of ,8. Clarkei (Proc. 
• ■‘^nys. Soo. Ediub., 1880, v.). (J?. E., Jimr.) 
