446 
Pectetj socialis, Moore, PI. 21, figs. 6, 7 (? 5 and 9). 
Pectcn socialis^ Moore, Quart. Journ. Geol. Soc., 1870, xxvi., p. 248, t, 11, f. 10. 
[Compare Pecten Ten, Woods, Proc. Linn. Soc. N. S. Wales, 1883, viii., p. 239.] 
Sp. Char. Shell suborhicular, small, both valves apparently alike, moderately 
convex, margins rounded, llorsal margin short, shortest on the anterior side. Umbones 
rather gibbous, pointed; ears small, triangular, flattened, the anterior the smaller of 
the two, apparently unornamented ; anterior and posterior slopes w'ell marked. 
Surface with very regular radiatcly curved striae, with four or five strong concentric 
undulations on the umbonal region. 
Ohs. The late Mr. Tenison Woods suggested that his Pecten psila might be this 
species, and Prof. Tate lias adopted * this view, but if the ears of Woods’ species are, 
as he describes them, radiately ribbed, the two shells cannot be identical. The curved 
radiating and very fine costae place JP. sociuUs iicmr the genus Camptonectes, Agassiz, but 
I have not seen any evidence of the e.vistcnco of the intercostal punctac. It reaches 
as much as one inch, in length by a half-inch in breadth, a shell of this size being in the 
cabinet of Mr. George Sweet, and the specimen figured by Moore seems to have been of 
similar dimensions. 
In general appearance P. socialis would also seem to fall within Meek’s genus 
Syncyclonema,-\ which was proposed for smooth compressed Pectens of Cretaceous and 
Jurassic rocks, such as “ cannot be properly included in the genus Pecten as restricted 
to such forms as as P. maximm." It is a compressed, nearly equivalve closed genus, 
with a short hinge-line, small ears, and no definite byssal sinus. Mr. Moore made the 
following remarks on his Wollumbilla specimen: — “The external ornamentation of 
this shell is not well preserved ; but it appears to have been nearly smooth, without 
visible concentric striae, but with depressed radiating ribs. lu general form it is not 
unlike P. rigidtis.X It is one of the most abundant sheila in the boulders from 
Wollumbilla, many specimens of all ages appearing on their fractured surfaces.” 
In PI. 21, fig. 5, a very small, imperfect, and apparently quite smooth Pectcn 
is figured, but without other distinctive features than its form. The interior of the 
valve only is seen. The posterior wing was very small, and obliquely rectangular, 
the anterior somewhat larger, with a slight byssal notch below it. The hinge-line 
w’as straight. This little fossil is perhaps related to the present species. 
Loc. Wollumbilla (The late Rev. W. R. Clarke; Q. Sweet' — 'Colin. Sweet, 
Melbourne) ; Walsh Eiver (Son. A. C. G-regory) ; PI. 21, fig. 5, Mitchell Railway 
Station (J. Falconer'). 
Pecten, sp. ind., PI. 21, figs. 7 and 9. 
Ohs. A small and apparently common Pecten, of which, the exterior has not 
been seen, in some of its characters resembles P. socialis, but departs from it in the 
relative size of the more or less flattened ears. The shells are suborhicular, with square 
flattened ears and a shallow triangular cartilage pit. The interior surface is smooth, 
but the shell is thin enough to show radiating strife, which become stronger towards the 
ventraLand lateral margins. They have much the appearance of the punctured radiations 
seen in the genua Camptonectes, and divaricate rather than radiate in a similar 
manner. The body of the shell appears to bear a series of concentric laminse (PI. 21> 
fig. 7). The points mentioned are clearly important features of the species, and it is 
* Proo. Aiistr. Assoe. A(tv. Sci. for 1888 [1889], i., p. 230. 
t Smithsonian Check-list of N. American Cret. Poss., 1804, p. 7 ; also Report TJ. S. Geol. Survey, 
Territories, 1870, ix.,p. 26. 
J J. Sowerby, Min. Con., iii., p. 5, t. 205. 
