"Curvilinear iron detail and imaginative roof profile."

That is neither a phrase from a graduate Vis Stud thesis, nor a description of your roommate's girlfriend. Rather, those qualities of the Harvard Square kiosk earned it a place on the National Register of Historical Places this week.

The kiosk came to public attention recently because of proposed MBTA plans to destroy it as part of the $500-million extension of the Red Line subway.

An architect's model of the Square as it will appear after the extension is completed in 1982 includes a newsstand in place of the subway entrance, and a triangular, tree-lined plaza in front of the Cambridge Savings Bank.

The MBTA, which owns the kiosk, may legally destroy it even though it is on the register. The transport authority will make its plan for the kiosk public at a meeting early next week.

The MBTA might do well to keep the kiosk. If it does, the National Park Service will grant half the funds for restoration, with the MBTA paying the rest. In addition, recently enacted tax incentives designed to encourage the upkeep and safety of historic places would defray part of the expenses. What the state agency will do about the development of its yards on Eliot St., next to the new Kennedy School of Government, seems less clear.

The site is to serve as a temporary station during the next four years of subway construction, but state guidelines demand an Environmental Impact Report and a public hearing to determine whether a planned adjacent development is harmful to the environment.

A number of concerned Cambridge residents have formed a community group to keep informed of government action on the development, but so far that action has been slow in coming.

State officials must decide soon whether it is the Commonwealth or the recently selected developer of the area who has responsibility for the preparation of the impact report.