5:2 
K. L. PRENDERGAST. 
The distinctive characters are the widely spaced concentric rows of 
spines combined with ihe elongated shape of the shell. 
Comparison xvith other species . — This shell appears most similar to 
■Strophalosia rarispina Waagen (1884, p. 645) but the pedicle valve of that 
:species has a slight median sinus and the spines are in two series. 
Strophalosia tenuispina Waagen. 
PI. vi, fig. 9. 
1884 . — Strophalosia tcjuiispiiia IVaagen, p. 654, pi. Ixiv, figs. 2-7. 
Material.— V.'W. A. 20451. One pedicle valve. Fossil Cliff, Irwin River. 
Fossil Cliff horizon. 
Diagnosis . — Shell circular to oval in outline, hinge-line equal to maxi- 
mum width, pedicle valve but slightly inflated, dorsal valve concave. Surface 
ornamentation finely lamellose with sparsely distributed oblique spines. 
Pedicle valve non-sinuate, area high, with Hat, narrow linear pseudo-delti- 
dium. S 2 uall scai' of attachment. 
Brachial valve with small linear area, surface ornamentation not known. 
Descrigytion . — This species is known by a single specimen of a pedicle 
valve fi'om the Irwin River. 
Dimensions of Valve. 
Height . . . . . . 17.81 
Afaximum width . . . . 21.81 
The specimen is rather weathered, but shows the fine spines; these are 
represented now only as rather Avorn bases; the spines are all tangential to 
the shell surface and some of them adpressed. They are arranged more or 
less ill concentric roivs, each row separated from the previous one and that 
folloAving by lamellae. On the lateral margins larger spines are develojied, 
and these show a curious marking, almost a facet developed on the ventral 
surface of each spine. Whether this is the effect of weathering it is im- 
possible to say. The spines, apart from their concentric arrangement, also 
shoAv a roughly (luincuncial arrangement. 
The area of this species is vei’v distinctive among Strophalosias, being 
flat and in the jilane of the commissure of the valves. It is interrupted by a 
very narroAV, parallel-sided pseudo-deltidium. 
Cowgyarison with other species. — For comparison of this species ivith 
Strophalosia etheridgei mihi, see account of that species. 
ETHERIDGINA Oehlert. 
1887. — Oehlert, in Fischer’s Manuel de Couchylogie, p. 1278. 
Genotype. — rrodncfiis complectcns Fth. fil., 1876, On an adherent Form of 
Produdf-'us and a small Spiriforina from Scotland. Quart. J. geol. Soc. Lord., 
p. 454, pis. xxiv, XXV. 
Diagnosis. — Shell small, concavo-convex, dorso-ventrally, Avith semi-oval 
marginal contour; generally as broad as long; hinge-line less than greatest 
Avidth of shell. Shell attached to foreign bodies by embracing spines or by 
cementation of ])edicle A'ah'e. Surface ornamentation of concentric undulat- 
ing Avrinkles. Area primarily present, Avith dental sockets and teeth. Muscle 
scars non-dendritie. 
