Travel Reference
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the size of a dinner plate, with irregular edges. One side of the fragment
gleamed silvery in the shafts of muted sunlight dancing down from the sur-
face, and he saw that its other side was creamy white, with a large reddish
stripe traversing one corner. There was no mistaking this shell. Somewhete
above him, a large ammonite had just died.
He dropped the piece of shell and warily rose to 20 feet to start his de-
compression stop, slowly turning 360's in lookout. During his second or third
rotation he saw a distant school of creatures coming in his direction. As they
approached through the shallow surface turbidity, he recognized them as
planispiral ammonites, species with large discoidal shells, all swimming
backwards with head behind. Some had shells more than a yard in diameter,
and all were countershaded: dark color on top of the shells, white beneath, a
camouflage evolved because it fools predators either above or below. Pachy-
discids, he thought, seeing the distinctive ribbed shells. They swam slowly
but purposefully, conveying a sense of power, like old battleships passing in
stately formation. They were not like the skittish, torpedo squids of his day,
which relied on speed to save their unprotected and succulent bodies from
becoming meals. The ammonites used their shells like ancient dread-
noughts, a streamlined but massive armor. He could now see their large,
octopus-like eyes as they passed by, the closer animals veering to avoid him,
the farther reaches of the school paying him no heed.
He watched the last of the large ammonites swim lugubriously into the
distance, finally to disappear, swallowed by the sea as they left his 50-foot
circle of visibility. He was nearing the end of his first decompression stop,
and as he watched the second hand on his chronometer sweep its slow arcs,
movement caught his eye. He saw another school of large ammonites just at
the limit of visibility, and once again he heard a piercing crack. He began to
swim toward this second school, the bright sunlit water warming his body.
The ammonites were careening and scattering as he approached, and
now he could see a larger, wraith-like shape among them. He backpedaled as
he watched the mosasaur feeding among the ammonites. It was relatively
small, only about 8 to 10 feet long, and its shape and head were quite famil-
iar to him. He was well acquainted with the monitor lizards of Pacific islands
