Cardabia bullarensis sp. nov.

Plate 90, figs. 3, 4 ; Plate 91, figs. 1-3

Material and occurrence. Twenty-three specimens from the northern en of Giralia Anticlin, Carnarvon Basin on Giralia Station, North West Division, Western Australia. Nine, including the holotype (WAM 73.361) and two paratypes (WAM 73.365, 73.366) are from the south side of the Bullara-Giralia road in the vicinity of the turn-off to Jubilee Bore at approximatly 22° 40' S., 114°, 13' E., and about 6.5 km south of the bore. Although the echinoids were not found in situ they have traces of white glauconitic lime mudstone adhering to them. Eleven reddish silicified specimens were found loose 400 m south of a white hill about 5 km south of Jubilee Bore at approximately 22° 39' S., 114° 14' E. NMV P31199 was collected by T. A. Darragh and labelled 'Wadera Calcarenite, float on E. side of Main N.-S. tract of C-Y Creek (due E. of bore and E. of fence, Open Country Paddock), Yanrey 188147', at approximately 22° 52' S., 114° 7' E. A further two crushed echinoids( P31227, 31228) are probably the same species. They are from the type section of the Wadera Calcarenite, Old Marilla Station at 22° 50' S., 114° 8' E.

Measurements. The dimensions of the holotype are : length 20 mm, width 17 mm, height 10 mm. Other specimens from the same locality range from 14 x 11 x8 mm up to 25 x 21 x 11 mm.

Description. Adapical and adoral surfaces flattened, with the ambitus uniformly rounded. Prominent plastronal keel which terminates in a slight anal rostrum ; anterior margin gently rounded at the ambitus.

Apical system in front of centre, disjunct, with three genital pores ; that of the madreporiste is lacking. Ambulacra composed of small pore-pairs not easily discernible in unweathered specimens. Adapically the small round pores are placed close together and separated by a granule. The pore-pairs in the paired ambulacra placed slightly en-chevron ; in ambulacrum III they are almost longitudinally directed.

Transversely oval periproct located just above anal rostrum. Subcircular, anteriorly located peristome with prominent phyllodes composed of deeptly countersunk pores. Test coated with coarse granules and relatively dense small primary tubercles. Adoral surface with dense plastronal tuberculation but tubercles absent in the phyllodes and ambulacra I and V.

Plastronal plating consisting of a relatively long labrum extending to the second ambulacral plate followed by a single large sternal plate extending to the fourth ambulacral plate. There follows a pair of episternal plates (the suture which separates them is only discernible with difficulty in the available material). The episternals are succeeded by a single plate, in the position of the point of the rostrum, and then two pairs of pre-anals. A subcircular subanal fasciole encloses the rostral plate.

Remarks. This new species is readily distinguished from specimens of Corystus dysasteroides in the Australian Tertiary by its smaller size, three genital pores, flat upper and lower surfaces, less prominent pore-pairs arranged en-chevron, subcircular peristome, coarser and more dense tuberculation, and the absenc of a frontal notch.