In Brooklyn, Suspicious Passenger, With a Tail It was a few minutes before 4:30 a.m. when the call came in: a suspicious passenger was aboard a Manhattan-bound subway train. Other riders were alarmed. The suspect was said to be making furtive movements. And there was something else: this suspect had a tail. Last Friday - yes, it happened to be the 13th - the straphangers on a late-night D train were startled to discover that a nonhuman creature was in their midst. An opossum, to be precise. The intrepid marsupial, which had apparently boarded after the train departed from its Coney Island terminus, had curled up beneath a seat, comfortably close to a radiator, as the train rattled through the wilds of Brooklyn. There were several reasons this was rather strange. For one thing, opossums tend to like trees. They are not big burrowers, although they have been known to venture below ground in search of food or warmth. And unlike rats or pigeons (often seen on A trains in the Rockaways), they do not commonly carouse within the city's mass transit system. But the opossum, as it turns out, is a nomadic creature - which perhaps explains its decision to hitch an interborough ride on the rails. And the animal disembarked only after some significant urging from the authorities. The D train was evacuated after arriving at the West Fourth Street station in Manhattan, where a group of police officers, armed with heavy-duty gloves and a canvas bag, were on hand to nab their perp. The officers were turned back, however, after the animal bared its teeth and snarled, the police said. This, apparently, was a job for the experts. The officers arranged for animal control agents to meet the train in a subway yard next to the Grand Concourse in the Bronx, according to Paul J. Browne, the chief police spokesman. Normal D train service was then resumed, after a 27-minute delay. Neither the Police Department nor New York City Transit keeps statistics on subway animal incursions. But officials from both agencies said that such an occurrence was rare. A wild animal? This is the first anybody could remember," said Charles F. Seaton, a transit authority spokesman, who sounded quite amused by the tale. Anecdotally, however, the opossum seems to have its predecessors. An official at the transit workers" union said he could remember seeing raccoons hanging around the D train platforms in the Bronx. One veteran subway worker recalled the presence of "subway cats" in the 1980s, but those, he said, frequented the tunnels, not the trains. Pigeons often fly into open train doors in the Rockaways, where the stations are near the beach. Rats, of course, might as well be considered permanent residents of the system. But opossums? "It's not surprising that one would wander into a train because they are so comfortable living around people," said Patrick Thomas, the general curator at the Bronx Zoo. It might have been drawn to the train by heat, or the smell of food. Mr. Thomas said he wondered if the opossum had slipped onto the train through an open door, before passengers came onboard. "They would look for a dark area where it's quiet," he said. There remains one prevailing mystery regarding this particular opossum: what exactly became of it? Officials from New York Animal Care and Control did not return repeated calls, and the city's health department, which oversees animal control, said that the group was not involved in the removal. Transit officials could shed no further light on the matter. The lesson for straphangers is clear: the next time you ride a D train, wear shoes.