. Bulletin of the British Museum (Natural History). 250. Fig. 9 Hemicytherura subulata sp. nov. Holotype OS 8300, $ right valve external lateral view, showing the arrangement of fossae. x260. Figured specimens. Holotype, right valve OS 7772. Paratypes (unfigured here, but see Ahmad 1977/?), left valve OS 7774, right valve OS 7773. Sample FCRM 2010, stream south-west of Mtwero; Lower Miocene. Other material. Sixteen single valves from samples FCRM 1738, 2010 ( OS 7784-5 and paratypes OS 7775-6), 2015. Also occurs in FCRM 2014. Description. Carapace small to medium-sized, with grea
. Bulletin of the British Museum (Natural History). 250. Fig. 9 Hemicytherura subulata sp. nov. Holotype OS 8300, $ right valve external lateral view, showing the arrangement of fossae. x260. Figured specimens. Holotype, right valve OS 7772. Paratypes (unfigured here, but see Ahmad 1977/?), left valve OS 7774, right valve OS 7773. Sample FCRM 2010, stream south-west of Mtwero; Lower Miocene. Other material. Sixteen single valves from samples FCRM 1738, 2010 ( OS 7784-5 and paratypes OS 7775-6), 2015. Also occurs in FCRM 2014. Description. Carapace small to medium-sized, with greatest height at anterior end and greatest width at middle; very fragile. Anterior margin modified externally by the ventrolateral frill but symmetrically rounded when seen from inside. Dorsal margin almost straight; posterior narrowly produced, giving a beaker-shaped appearance in internal view. Seen obliquely from inside, ventral margin almost straight, sub-parallel to dorsal margin, but in external view completely hidden by the overhanging lateral frill. Frill starts in ventral half of anterior margin, gradually increases in width and terminates abruptly anterior to caudal process. Lateral surface smooth except for frill. Three fine longitudinal ridges occur ventral to the frill. One runs just below top of the frill for its full length; the others are much shorter, and stronger in the posterior half than anteriorly. Internally, duplicature moderately wide; vestibule absent. Ten or eleven normal pore canals divide the frill into compartments; these canals are very much like marginal ones, and have been described by Maddocks (1966) as 'thick straight pore canals', while Hornibrook (1952) described those in Manawa as 'septa in the friir, and Ishizaki (1973) refers to them simply as 'marginal pore canals". Three marginal pore canals visible. Four small adductor muscle scars in a vertical row, with three AHMAD, NEALE & SIDDIOUI larger frontal scars placed dorsally, the low
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