Wataru Ishijima was a paleontologist and geologist and one of the most prolific researchers of fossil calcareous algae, an algae mostly or partly composed of calcium carbonate.
Wataru Ishijima ( , Ishijima Wataru, 1906  1980) was a paleontologist and geologist. Ishijima was one of the most prolific researchers of fossil calcareous algae. Calcareous is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. 
