My search for the perfect pet ended when Mother Nature sent me a snapping turtle.

The three-inch beast was struggling along the center line of an Eastern Shore highway in the noonday sun, far from any creek or moist ditch. He was hot to the touch and the algae on his back had dried and died.He seemed to be about to join them.

He also looked starved, with the flesh drawn up inside his shell and his neckbones showing, but when I poured water over him he swelled like a toad in heat.

It wasn't until then that I realized how ugly he was. His beady little eyes were set in a big mean head on a snaky neck as long as the rest of him. The shell had three rows of blunt spines and the tail was sawtoothed like a dinosaur's. Every part that wasn't armored was covered with warty tubercules.

I put the turtle in the back of the van and drove on. Every few minutes I would look down and find him making his way toward my ankles with his oversize jaws agape. Shutting him up in an empty carton of Sour Sam lemonade saved my ankles and supplied his name. The rascal may in fact be Sour Samantha; even naturalists have a hard time sexing them without a can opener.

The Peterson field guide described snappers as having "short tempers and long tails" and abandoned the dry neutrality of science to opine that they are "ugly both in aqppearance and disposition."

I had thought to release him in a pond, but Sam was too mean and ugly to part with. Ugliness is endlessly facinating.I can grow tired of Renoir's beautiful Girl with a Watering Can , but never of the cruel self-portraits of Van Gogh.

All my previous pets have had personality problems. Blackie the dog was a caricature of spineless, slobbery devotion. There has been a long line of cats that were moody and/or incontinent. Tropical fish are exquisite, delicate and boring. Hamsters stink. Gerbils are dull. Don't talk to me about birds.

In Sour Sam I have a pet that is dependable in appearance and deportment: ugly as homemade sin and meaner than a junkyard dog. Our relationship is straightforward: We both covet my fingers.

Sam's wants are simple. He is content so long as he has a wet place to lurk in and something to snap at. I put him in a 20-gallon aquarium and tossed in some dollar-a-dozen goldfish culls, along with a pair of crayfish and some snails to clean up after his meals, which are as messy as they are sudden. He sits on the bottom of the tank, quiet as a stump, with his head tucked into his carapace. He may lie there for an hour until the fish he wants swims by; the strike is faster than the eye can follow.Scales and fragments go flying.

The setup took a little fine-tuning. Sam ate the snails and the two crayfish fought until there was one crayfish with one claw, and then Sam took care of him. After extensive and expensive experimentation it was concluded that anything that went into the tank, inanimate or otherwise, was odds-up to wind up inside Sam, including marbles.

And the kids had an adjustment problem.No sooner would they settle on names for the goldfish than Sam would start chomping his way through the roster. It added nothing to the enjoyment of breakfast to listen to aggrieved offspring calling the roll of the slain:

"Farrah's gone."

"Yues. And Darth and Sniffles. And half of Blinky."

They pretended to be talking to each other, but the sides of their mouths were pointed at me. I would remind them it was a turtle tank, not a goldfish bowl, and gave little lectures on the nature of nature, which fell flat. From time to time they reprieved fish and hid them in their rooms. They got over it after a few years.

The temptation to overfeed Sam is strong because his table manners are so spectacular. He will wolf six-inch nightcrawlers until he is tight as a tick. s"You'll know he's getting fat if his skin starts pooching out when he tries to tuck his head and legs under his carapace," said Mike Davenport, one of the National Zoo's reptile men. Sam's skin pooches out, sure enough. It might be said to balloon.

"They're great pets," Davenport went on. "They'll eat anything, and they're very durable. A friend of mine picked up one that had been run over in the road. He was all busted up, but the vet patched him with fiber glass and he was good as new."

After a few years Sam outgrew the 20-gallon tank, and now, at six inches, he's crowding a 40-gallon one. Turtles are measured by the length of the top shell, which is deceptive. As he doubled in length Sam increased tenfold in weight, and now hefts about two pounds. The record for a captive snapper is over 80 pounds. But they're slow growers -- Sam may be ten years old -- and if he gets too big to handle, he'll be good to eat.