If your last name is Davis, Jones or Thomas, there's Welsh on your pedigree chart.

The same applies if it's Phillips, Bowen, Parry, Lewis, Pritchard, Pugh, Bennion, Price, Rees, Owens, Powell, Griffiths, Evans or any of several other relatively common surnames.And if you have one of the above names, the odds are good that a Brigham Young University languages professor is interested in speaking with you. Ronald Dennis is interested in the stories found in diaries, journals and other records of 19th century Welsh immigrants because, in many ways, they are more enlightening than official documents.

For nearly 20 years, Dennis has absorbed himself in Welsh history, particularly in early Welsh history of The Church of Jesus Christ of Latter-day Saints. His most recent book, "The Call of Zion: The Story of the First Welsh Mormon Emigration," demonstrates his commitment to mid-19th century Welsh LDS writings.

He teaches Portuguese, but an examination of his office reveals his dominant interest in Wales. The time-worn books wedged in his front bookcases are in Welsh, many of them welcome gifts he has received on his sojourns to Wales. The familiar red dragon that identifies Wales and pictures of the Welsh countryside decorate his office space. A wall-to-wall row of crammed binders demonstrates various stages of his work with the translation of Welsh records.

He even traveled to Salt Lake City to witness Utah Gov. Norm Bangerter's declaration of March 1 as St. David's Day for Utah. David, the patron saint of Wales, is being honored this year on the 1,400th anniversary of his death.

Dennis' interest in Wales emerged in the late 1960s when he learned that his Welsh great-great-grandfather, Captain Dan Jones, was an early Mormon convert who received the last recorded prophecy by LDS prophet Joseph Smith just before the religious leader's martyrdom.

As he began to study his own Welsh ancestors, Dennis discovered that no comprehensive study existed of early Welsh Mormons. He realized a treasure trove of information was ready for excavation.

Dennis' Welsh publishing includes books, articles and translations. His overriding interest now, however, is writing a book in honor of the sesquicentennial of missionary work in Wales, which will be commemorated in 1990. The focus will be on the 1840s and 1850s, when about 10,000 people were converted to the Mormon religion in Wales. He then hopes to trace their migration to the United States and their trek westward to the Salt Lake Valley and report where they settled and what became of them.

The book will include adventure, including a report of Dan Jones' successful foil of three attempts on his life within a 36-hour period; conversion stories; defenses of Mormonism found in "Prophwyd Y Jubili" and "Seren Y Saint" ("Prophet of Jubilee," "Star of the Saints"); and a focus on certain individuals such as John Parry, first conductor of the Mormon Tabernacle Choir.

"I've got considerable information, but I know I'm missing valuable early history that is no doubt written in journals and records that are probably gathering dust in attics, in storage boxes or on bookshelves. You would probably be amazed at how many people in the Intermountain West have Welsh in their backgrounds. Some communities, such as Malad, Idaho, originally were settled as Welsh towns. I am fairly certain many of them have inherited records of their Welsh ancestors."

In his searching, Dennis has often found Welsh history by happy accident. Recently, he visited the Clover Valley, south of Tooele. He had heard a woman there had some Welsh Mormon publications. She didn't, but she referred him to a neighbor whose ancestor was a Welshman named William Ajax.

"I had never heard of William Ajax, but I discovered he was the last editor of Zion's Trumpet, a Welsh Mormon publication. He had written a 400-page journal, and there was a gold mine of information. I found out that `Zion's Trumpet' had ended in 1862 because Ajax wanted to come to Salt Lake Valley and couldn't find anyone to take over the publication. I couldn't really tell the Welsh story very well without William Ajax. Here was wonderful material the family couldn't even understand because much of it was in Welsh." (Dennis teaches Spanish and Portuguese, but one of his first tasks when he became interested in Wales was to learn to speak and read the difficult language.)

"I've come across a dozen diaries by beating the bushes," he says. "But I wish people would come forth and put their records in repositories. At BYU, for example, you get a copy back and you can specify the terms under which the original record can be seen."

While Dennis has enough material to write several books, he would like the sesquicentennial book to be as complete as possible. "It's the researcher in me, I guess, " he says.

His own name, Dennis, is German, but he quickly affirms that he is one-eighth Welsh.

"I feel as if I'm researching an area as clean as fresh snow," he says. "I find it exciting to be able to have the corner on some research that captivates me."