THE CAINOZOIC CIDARIDAE OF AUSTRALIA. 
Europe and of India to the Miocene of Europe, probably belong 
to Prionocidaris, though none is placed by their authors in that 
genus. 
Prionocidaris scoparia sp. nov. 
Plate XII, figs. 10, 11 ; Plate XV, figs. 28-30. 
Test large, tall and slightly depressed abactinally. Ambulacrum narrow 
and wavy, ambulacra! plates usually with two vertical rows of small miliary 
tubercles, making four rows present in interporiferous area ; poriferous zone 
slightly sunken ; pores conjugate, oval, close together. About fifteen ambu- 
lacral plates adjacent to largest interambulacral plate. Seven coronal plates. 
Boss broad, uncrenulated, with perforate mamelon slightly contracted at neck. 
Scrobicules shallow, circular towards apex, elsewhere elliptical. Scrobicular 
circle bounded by a ring of tubercles which does not overhang margin of 
scrobicule. Except in abactinal region, the rings merge together ; between 
scrobicules near actinosome they tend to disappear. Median area of inter- 
ambulacra very narrow, even near ambitus ; only slightly depressed at suture ; 
covered with closely packed miliaries of unequal size. No pits or grooves in 
horizontal or vertical sutures. 
Remarks on Tests . — The syntype from Mt. Gambier, in 
common with other specimens which we have seen, shows that 
the test is large and high ; in the syntype from Aldinga the 
test is nearly complete but considerably flattened by crushing 
in situ (PI. IX, fig. 10). Fortunately a spine has been preserved 
on this test ; it lies across the apex not far from the mamelon 
from which it was detached. This spine corroborates our 
earlier determination of isolated spines of this species. 
Measurements.- Syntype (interamb zone), from Knight’s Railway Siding 
Quarry, Mt. Gambier, S.A. (Mines Dept. Viet. Coll.) : — height of test, about 
64 mm. ; width of interamb area at ambitus, 38 mm. ; width of interamb 
plate in region of ambitus, 21 mm. ; height of plate, 12 mm. ; width of amb 
plate, 3.5 mm. Syntype from Aldinga, lower beds (Tate Coll.) : a nearly 
complete test. Present diameter of test, 75 mm. ; height, considerably 
reduced by crushing, 32 mm. ; diameter of apical system, about 20 mm. ; 
diameter of peristome, about 22 mm. ; width of amb, 8.5 mm. ; width of 
interamb area at ambitus, 38 mm. ; width of interamb plate in region of 
ambicus, 20 mm. Spine without apex lying on test 38 mm. long; base to 
end of collar, 8 mm. ; diameter of ring, 6 mm. ; greatest diameter of shaft, 5 mm. 
Spines long, stout, slightly tapering, usually cylindrical; some widened 
and much flattened on both sides towards apex. Ring finely milled ; diameter 
much greater than that of shaft ; no narrowing of shaft above ring. Shaft 
ornamented with thorns, all long or all short, scattered or arranged linearly. 
Extremely fine granules cover shaft between thorns. Spines with rounded 
shafts have apex flared, forming depression surrounded by pointed terminals 
of granular ornament of spine. Flattened spines have no terminal depression ; 
apex composed of projections of ornament ; shaft terminates as though cut 
across at 45 degrees to its length. Localities. — Waurn Ponds, Nelson, Mount 
Gambier and lower beds, Aldinga. 
Measurements. — Paratypes (spines), both from lower beds, Aldinga : length 
of thorn-bearing spine, tip imperfect, 100 mm. ; width at ring, 6 mm. , width 
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