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Mentzelia kawhiana (LPC10_1285) in a gritstone from scree in Highfield Farm: ventral valve.
Description of Mentzelia kawhiana (Trechmann 1918): Shell rather wider than long, the anterior margin gently rounded. The ventral valve is somewhat swollen and arched, the beak tapering gradually, the dorsal valve is almost flat, and the margin of the valves lies nearly in one plane. The area is less than the width of the shell, and seems to have been rather high. The ventral valve has a shallow, rounded, rather broad, median sulcus, with about seven very faint and narrow, lateral, rounded ribs on each side of it: these do not continue to the beak, and are absent from the lateral portions of the shell. The dorsal valve bears a very faint, flattened, triangular, median fold and about seven very faint, narrow ribs on each side of it which do not reach the beak. The lateral portions of the shell towards the hinge-area are smooth. Length--25 ram. ; width--31 mm. |
Mentzelia kawhiana
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