A relatively rare large fossil of an extinct and little-known whale has been found on the St. Mary's County shoreline and is being prepared for a public showing next month at the Calvert Marine Museum at Solomons Island.

Museum officials are mum on the subject until then, but the discovery last month of a 50-pound "cetothere" skull by amateur fossil hunter Luther Lorr, has sent a ripple of excitement through the staid, calm world of fossils and their collectors.

"They're moderately rare and they're largely unstudied," said David Bohaska, a paleontologist with the Smithsonian Institution who has seen the fossil and tentatively identified it as an 8-million-year-old cetothere, an ancestor of modern fin whales.

Cetothere fossils are found worldwide, and similar skulls have been found before in Southern Maryland, Bohaska said. But little is known about the baleen whales that lived on what used to be open ocean areas of what is now Chesapeake Bay, Bohaska said.

"It's a unique find and it's never been found in St. Mary's County. It's fabulous," said Elinor Cofer, a veteran fossil hunter and collector who has been leading fossil trips in the area for 15 years. Cofer, who is in her eighties, said she has never come across such a fossil in St. Mary's during her 25 years of collecting in Southern Maryland.

When she saw the fossil, Cofer said, "I almost dropped dead. It's black, glossy. It's huge, and it's rare." Cofer said she persuaded Lorr to consult a paleontologist about what he had found. "It's a very, very impressive fossil," she said.

Lorr, a middle school teacher who has been fossil-hunting for several years, was circumspect last week as he recalled the day a month ago when he saw the fossil on the Chesapeake Bay coastline. (Paleontologists and local fossil collectors have asked that the site of the find not be identified to prevent people from flocking to it.)

"I thought, `Okay, I found something unusual. No big event,' " Lorr said.

The fossil is 24 inches by 32 inches. Compared with most of the fossils he has collected, Lorr said, it is big.

"It doesn't fit on my coffee table," Lorr laughed.

Stephen Godfrey, the curator of paleontology at the Calvert Marine Museum, said last week that he is not prepared to discuss the fossil or provide a photograph of it because it is still being cleaned and prepared for showing. Although Bohaska said the fossil is that of a cetothere, Godfrey said the fossil has not been identified. But he acknowledged that it is "a rare specimen" of a whale skull.

In the last 50 years, many fossil pieces of cetotheres have been found in many places. However, Bohaska said, big, important pieces such as the one found in St. Mary's have been rare. The lack of a comprehensive collection, and the size of the whales, have made it difficult to study cetotheres, he said.

"Now we've been finding better material," Bohaska said.

"There's been a gradual accumulation over the decades of these skulls. I think we've gotten to the critical mass now that we can learn something about the baleen whale from the St. Mary's formation to better our understanding," Bohaska said.

Calvert Marine Museum has about 20 large whale skull and porpoise fossils in its collection, according to Doug Alves, the museum director.

"Considering it's [new cetothere fossil] 1/20th of the collection . . . it's not a dime a dozen," Alves said.

So important is the new fossil that display space for it will be made in the museum's paleontology hall, Alves said.

CAPTION: This drawing depicts what scientists think a cetothere looked like. The fossil found in St. Mary's County is believed to be from a cetothere, a whale species that lived 8 million years ago.