The purpose of this book is to provide sketches and descriptions of many types of shell structures to aid the architect or engineer in the selection of a structure for a particular use. No claim is made for completeness. Drawings have been used rather than photographs, first because of the limited number of photographs available, and second, because there is always a reluctance on the part of the architect to use something already built because it would seem like copying. Only the structural features are shown in the sketches and details such as windows, gutters, fascia members, etcetera, have been omitted. The criterion has always been to picture the shell after the concrete has been complete but before the brick, stone, windows, or roofing is placed. Most of the nomenclature is standard in the literature but some of it was devised by the writer to fit gaps for which satisfactory terms were not available. In illustrating shell types, many obvious structures have been omitted because they are so similar to the basic types. The criterion for showing examples has in all cases been its usefulness as an architectural or structural unit of construction.