Turner indicated a category for each plate of the Liber Studiorum according to his proposed classification of landscapes. The categories are: Mountainous, Historical, Pastoral, Architectural, Marine, and EP. Turner never explained the meaning of 'EP', and suggestions which have been variously proposed include 'Epic Pastoral', 'Elevated Pastoral' and 'Elegant Pastoral'.
Ruskin 's references in Modern Painters I are almost exclusively restricted to the Mountainous, Pastoral, Architectural, and Historical plates. He rarely refers to plates of the Epic Pastoral category (possibly because many of these are clearly influenced by Claude) and (surprisingly) never refers to those of the Marine category.