. Bulletin of the British Museum (Natural History), Geology. 100 SMITH, PAUL, GALE & DONOVAN 10-11-5mm in diameter (Fig. 35). The interambulacral plates are considerably wider than tall; at the ambitus mean plate height is 24% of plate width (SD = 1-5; N = 10). Each inter- ambulacral plate has a small primary tubercle at the centre and up to two other secondary tubercles of much the same size at the ambitus. A further two tubercles, very much smaller than the three principle tubercles, may be present towards the adradial edge of the plate. These are not aligned with the other tubercles. Th
. Bulletin of the British Museum (Natural History), Geology. 100 SMITH, PAUL, GALE & DONOVAN 10-11-5mm in diameter (Fig. 35). The interambulacral plates are considerably wider than tall; at the ambitus mean plate height is 24% of plate width (SD = 1-5; N = 10). Each inter- ambulacral plate has a small primary tubercle at the centre and up to two other secondary tubercles of much the same size at the ambitus. A further two tubercles, very much smaller than the three principle tubercles, may be present towards the adradial edge of the plate. These are not aligned with the other tubercles. There are about four ambulacral pores opposite each interambulacral plate at the ambitus, but only three subambitally. PERISTOME. This is circular in outline and slightly sunken and is 25-31% of the diameter (mean = 27%; SD = 2T; N = 64). There are distinct gill slits and although these are shallow they are sharply defined. No concentration of ambulacral pores or dense tuberculation is developed around the peristome. PERIGNATHIC GIRDLE. There are well-developed internal auricles, which remain unfused perradially. Internally there are also 10 well-developed ridges lying at the adradial edge of interambulacral columns; they are present only on the oral surface and are best developed Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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