A memorial service for Sylvanis A. Tyler Sr., 71, a mathemetician who worked at Argonne National Laboratory for 34 years, will be held at 2 p.m. Monday in Olivet Baptist Church, 405 E. 31st St. Mr. Tyler died Wednesday in his South Side home. He was best known for his work on the construction of mathematical and statistical models of biological phenomena. He published more than 75 articles in journals. He joined Argonne as biostatistician in 1946 after serving with the Army Signal Corps in Italy during World War II. He retired in 1980 but remained active as a statistical consultant to Argonne, the Universities of Maryland, California and North Carolina and the U.S. Department of Interior. He also taught at Tougaloo College in Mississipppi and at Alabama A. & M. College in Huntsville. He is survived by a daughter, Sylvia Langford, and a son, Sylvanus Jr.