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longer than wide; hinge-line variable in length but never as wide as the shell; area 
well marked, elongately triangular ; dcltidium conspicuous, convex ; septum short ; 
renal impressions broadly oval ; internal surface highly granular. Surface of the ventral 
valve concentrically laminated, and giving rise to numerous adpressed tapering spines, 
which, when worn off, leave the valve covered by a series of short, blunt, somewhat 
projecting tubercles ; surface of the dorsal valve similarly ornamented, but the concen- 
tric laminae appear to be smaller and closer together ; near the front edge of the valve the 
lamellae become very close and numerous, and assume a strongly imbricated appearance. 
The greatest concavity of the dorsal valve is just below or in front of the hinge-line, where 
it appears to become much pressed in. The shell at times assumes a slightly irregular 
aspect, with an inclination or oblique tendency towards one side or the other; the front 
margin is rounded and continuous, and shows no indication of an indentation or sinuosity. 
Ohs. The identity of this Indian species with shells from the Bowen River Coal 
Tield was based on certain individuals from the latter, possessing, amongst other 
characters, very concave dorsal valves. This sepiaration was made, to some extent, on 
the advice of the late Dr. Davidson, but it was hinted that perhaps the one might prove 
to be a variety of the other.* The following remarks on this subject were made : — 
“Notwithstanding the flat valve of typical specimens of S. Clarkei, it is just possible 
that it and the shells now referred to S. G-erardi, with the concave dorsal valves, may 
after all be one and the same On the one hand we have a series of dorsal 
valves, all flat, and no ventral valve attached {—S. Clarlcei) ; on the other hand, a number 
of bivalve examples, with very concave dorsal valves (?=S. Gerardi).” It was 
subsequently shown,t through specimens obtained by Prof. A. Liversidge from the Darr 
Hirer,! that the two species were in all probability distinct, a point which I think now 
capable of proof. In contradistinction to S, Clarkei, the valves of &. Gerardi are both 
densely spined ; the dorsal valve always very concave ; the form more irregular in 
outline and smaller, the area wide, short, and triangular ; spines long, pendent, and 
3-dpressed to the shell ; and the surface of both valves very concentrically frilled ; but 
particularly noticeable amongst these arc the concave dorsal valves, and the short, high 
triangular area in the ventral valve. 
The internal structure of the dorsal valve has always been wanting to complete 
the comparison, but this is now supj)lied by a Tasmanian specimen in the Australian 
Museum, which I believe to be this species. The broadly oval forms of the renal or 
Vascular impressions resemble those of S. Glarhei, rather than /S. Jukesii, whilst, on the 
contrary, the short septum indicates a resemblance to the latter. The deep depressions 
CM. each side the septum in S. Clarkei are quite absent, so is the transverse ridge 
separating the upper from the lower pair of these, and probably the support of the 
^dductor muscles. The concavity of the dorsal valve varies, to some extent, in different 
individuals, but it is always very apparent. The hinge-line also varies in length, long 
in some examples, short in others, although, as before stated, it never extends the whole 
^idth of the shell. 
It would appear, therefore, from the foregoing remarks that in the Permo 
Carboniferous rocks of this Continent and Tasmania, at least three species of Stroplialosia 
^I'c met with, as originally described by the Writer. 
_ The resemblance of the Australian examples of 8. Gerardi to Prof. King s 
ndian type is very marked, both in outward shape, nature of the spines, form of the 
^ ^al valv es, and the area. 
* Proc. R. Phys. Soo. Ediiib., 1880, v., p. 29S. 
t Journ. R. Soo. N, S. Wales for 1883 [1884], xvii., p. 87. 
t Locality doubtful. {E.L.J.) 
