Charles E. Mohr and Thomas L. Poulson, HB, 232pp, McGraw-Hill Book Company and The World Book Encyclopedia (1966)

Part of the World Book Encyclopedia's series - 'Our Living World Of Nature'. The book covers the wide variety of life found in caves. It is an illustrated volume with over 100 trye-colour photographs, 50 duotone and black-and-white photographs.
The book is aimed at non-scientists and non-cavers, and so it is written with an introduction to how caves are formed and how they are explored.
A wide variety of cave life is covered, including mammals, reptiles, insects fish, crustaceans and salamanders. The book also explains how built-in "biological clocks" synchronise the behaviour of cave inhabitants with seasonal changes above ground.