Pterosoma planum

Lesson, 1827

Body length to 80 mm. Trunk expanded as large, flattened and oblong disk. Proboscis arises ventrally beneath the frontal margin of the disk, and the tail extends from the posterior end, tapering down to a narrow filament. Shell nearly flat, divided down the midline by a low ridge, and located on the dorsal surface of the visceral nucleus. While swimming, the visceral nucleus is elevated and the gills are exposed. When probed, the nucleus is retracted into a depression in the dorsal surface of the disk.
This species is not present in the Atlantic, but is included here for comparison with the other genera of Carinariidae.

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