spectre-tortoise

For while no spectator can deny their claims to a most solemn and superstitious consideration, no more than my firmest resolutions can decline to behold the spectre-tortoise when emerging from its shadowy recess; yet even the tortoise, dark and melancholy as it is upon the back, still possesses a bright side; its calipee or breast-plate being sometimes of a faint yellowish or golden tinge.

The Piazza Tales Herman Melville 1855