Since bikinis consist (by definition) of two pieces--a top and a bottom--a great deal more resolution and detail is required to accurately describe them. To prevent ambiguity we use the term soutien-gorge to refer to the bikini top in a generic sense, and the term culotte to refer to the bottom.
A wide variety of soutien-gorge and culotte exist. Popular literature uses a wide range of terms generically--tops are called halters, bras and blouses, and bottoms are called shorts, panties and briefs--with the effect of losing any finer resolution. The definitions and illustrations advanced in Bikini Science distinguish over two-dozen individual species of each in order to facilitate analysis.
Various drafts of these symbols for bikini tops and bottoms have evolved, from early hand drawings (1, 2), to Hypercard drawings of top (3) and bottom (4), to the icons used in the website.
Click on Costumes on the Main Menu and then Soutien-gorge or Culotte to see the latest incarnations of these symbols. For more on the concept of genus and species of swimwear see BSD8803.
Judson Rosebush, Bikini Science Hypercard Stack, 1988. 4 pictures.