. Bulletin of the British Museum (Natural History), Geology. LATE CAMPANIAN-MAASTRICHTIAN ECHINOIDS 227 two to three larger peribuccal pores in ambulacrum III, four to five in ambulacra II and IV, and three to four in ambulacra I and V. The interambulacra are biserial to the apex, although they become extremely narrow, especially posteriorly. On the oral surface there is a short, broad labral plate followed by a series of 5 alternating triangular-shaped plates which either just or almost reach the opposite suture (Fig. 77). Further towards the posterior the columns become more typically biseri
. Bulletin of the British Museum (Natural History), Geology. LATE CAMPANIAN-MAASTRICHTIAN ECHINOIDS 227 two to three larger peribuccal pores in ambulacrum III, four to five in ambulacra II and IV, and three to four in ambulacra I and V. The interambulacra are biserial to the apex, although they become extremely narrow, especially posteriorly. On the oral surface there is a short, broad labral plate followed by a series of 5 alternating triangular-shaped plates which either just or almost reach the opposite suture (Fig. 77). Further towards the posterior the columns become more typically biserial. The peristome is oval, slightly more than twice as wide as long, and lies at the base of the anterior sulcus, some 15-18% of test length from the anterior (mean = 17%, SD = 1-2%, N = 11). The peristome faces forward and is visible in anterior view. The labral plate hardly indents the posterior of the peristome. The periproct is oval, typically about 70% as wide as tall, and is strongly overhung so that it is visible from the oral surface but not from the apical surface (PI. 31, figs 8, 9). The test beneath the periproct is indented and there are two projections on either side. The periproct opens between interambulacral plates 5 and 10, the lower plates being strongly curved. The periproct lies low on the posterior surface and the distance to the base of the periproct from the lower surface is some 18-27% of the test height. Tuberculation is fine and uniform throughout, except along the inner (interambulacral) margin of the frontal sulcus where a double or triple row of noticeably larger tubercles is developed. There is no trace of a lateral fasciole to be seen. Oral tubercles are slightly larger than adapical ones, but there is no real difference in size between the tubercles of the plastron and those of the latero-ventral regions. The oral ambulacra appear to be tubercle-free. Remarks. This species is relatively common at certain levels in Jebel Rawdah. It co-occurs with
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