. Bulletin of the British Museum (Natural History), Geology. 1 mm Fig. 69 Camera lucida drawings of apical disc plating in Hemiaster from Wilmington: a, H. -I bufo, ; b, H. nasutulus, gate isopores with slit-like pores connected by a narrow, low ridge. The petals are open and unconstricted distally (Fig. 70a). The posterior paired ambulacra are shorter than the anterior petals, measuring 57-67% of the anterior petals (mean = 62%; SD = 4-9; N = 9) and extend 50% of the distance to the ambitus. They are straight and form an angle of about 75° to the posterior. They measure 17-22%
. Bulletin of the British Museum (Natural History), Geology. 1 mm Fig. 69 Camera lucida drawings of apical disc plating in Hemiaster from Wilmington: a, H. -I bufo, ; b, H. nasutulus, gate isopores with slit-like pores connected by a narrow, low ridge. The petals are open and unconstricted distally (Fig. 70a). The posterior paired ambulacra are shorter than the anterior petals, measuring 57-67% of the anterior petals (mean = 62%; SD = 4-9; N = 9) and extend 50% of the distance to the ambitus. They are straight and form an angle of about 75° to the posterior. They measure 17-22% of the test length in length (mean = 19%; SD = 1-7; N = 9) and stop slightly before the peripetalous fasciole. The two columns of pores are approximately equal and are composed of elongate, conjugate isopores 0-7-0-8 mm in width at 30 mm test length. There are 10 pores per column in an individual 18-5mm in length, rising to 17 or 18 in individuals 29-34mm in length. These petals are open distally. Adorally, larger isopores with a circular attachment area and a bulbous interporal partition are found. There are 3 isopores per column in ambulacrum III, 4 or 5 per column in ambulacra II and IV and 3 or 4 per column in ambulacra I and V. INTER AMBULACRA. The interambulacra are raised adapically and the posterior inter- ambulacrum is particularly raised, forming a keel behind the apical disc. On the oral surface. fasciole peristome labrum. 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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