| Leptostylochus gracilis Kato, 1934 | 1934 or earlier | | | autumn numerous specimens of a planarian were discovered underneath stones in somewhat brackish water on the shore near the Mitsui Institute of Marine Biology. |
| Stylochoplana amica Kato, 1937 | Mar 1934 | | | single specimen found by Mr. S. Suzuki in an aquarium, in which were kept a number of limpets, Patelloida schrenckii. |
| Notoplana japonica Kato, 1937 | 1934-1936 | | | a number of specimens collected from the undersurface of stones embedded rather deeply in the sand at the low tide-mark during spring and summer. |
| Discocelis japonica Yeri & Kaburaki, 1918 | 1934-1936 | | | |
| Hoploplana villosa (Lang, 1884) | May 22, 1936 | | | two specimens. In Japan, it is usually found on a bryozoa, Microporella ciliata (Pallas). |
| Pseudostylochus elongatus Kato, 1937 | 1935-1936 | | | large number of this planarian were obtained near the low tide-mark in the spring. |
| Planocera purpurea Yeri & Kaburaki, 1918 | May-Jun 1936 | | | 5 specimens collected. |
| Neoplanocera elongata Yeri & Kaburaki, 1918 | Jul 10, 1934 | | | single specimen at Susaki near the low tide-mark. |
| Cestoplana lactea Kato, 1937 | Jul 20, 1935 | | | single specimen near the low tide-mark. |
| Cestoplana rubrocincta (Grube, 1840) | Apr 1935 | | | single specimen under a stone in tide-pool. |
| Pseudoceros gratus Kato, 1937 | Mar 25, 1934 | | | single specimen of this splendid Pseudoceros found by Mr. J. Ishida who found it on the stone in the tidal zone in front of the Institute.. |
| Pseudoceros luteomarginatus Yeri & Kaburaki, 1918 | Jun 28, 1934 | | | two specimens. |
| Cycloporus papillosus (1) Sars, 1878 | 1934-1936 | | | numerous specimens identical with the Misaki form of Cycloporus papillosus were found in the summer on compound ascidians between tide-marks. |
| Prosthiostomum marmoratum Yeri & Kaburaki, 1918 | Jun 28, 1935 | | | two specimens. |
| Prosthiostomum siphunculus (Delle Chiaje, 1822) | 1934-1936 | | | fairly common in summer at Susaki. |
| Stylochoplana parasitica Kato, 1935 | 1935 or earlier | | | found in the pallial groove of Liolophura japonica var. tessellata, a common chiton occurring between tide-marks in the vicinity of the Mitsui Institute of Marine Biology near Shimoda. |
| Stylochus ijimai Yeri & Kaburaki, 1918 | 1932-1933 | | | common on the Pacific coasts of Japan in spring and summer. Often it attacks young oysters. |
| Notoplana delicata (Yeri & Kaburaki, 1918) | 1932-1933 | | | fairly common in the neighborhood of the Institute throughout the year. |
| Notoplana humilis (Stimpson, 1857) | 1932-1933 | | | one of the commonest species on the Pacific coasts of Japan and is found throughout the year. The color of its body is very variable but generally gray, brown or black. |
| Stylochoplana pusilla Bock, 1924 | 1932-1933 | | | in the mantle cavity of Monodonta labis Linné, a common sea snail occurring between tide-marks, was found a planarian identical with Bock's Stylochoplana pusilla from the corallina-formation in front of the Misaki Marine Biological Station. |
| Susakia badiomaculata Kato, 1934 | 1932 | | | single example of this interesting species was obtained between tide-marks in the autumn of 1932. |
| Planocera reticulata (Stimpson, 1855) | 1932-1933 | | | found in abundance in this district and Misaki all the year round; multi-tenticular forms often occur. |
| Callioplana marginata Stimpson, 1857 | 1932-1933 | | | Fairly common in summer. |
| Pseudostylochus fuscoviridus Kato, 1934 | 1932-1933 | | | found in summer together with Pseudostylochus obscurus on the underside of stones in the tidal zone. |
| Pseudostylochus obscurus (Stimpson, 1857) | 1932-1933 | | | very common in this district all the year round, and appears to be of fairly wide distribution in Japan. |
| Pseudoceros atropurpureus Kato, 1934 | May 13, 1933 | | | single specimen of this new species was obtained near low tide-mark. |
| Pseudoceros micropapillosus Kato, 1934 | 1932-1933 | | | very common between tide-marks in spring. |
| Pseudoceros susakiensis Kato, 1934 | May 1933 | | | two examples obtained between tide-marks. |
| Pseudoceros reticulatus Yeri & Kaburaki, 1918 | 1932-1933 | | | common in summer. |
| Thysanozoon brocchii (Risso, 1818) | 1932-1933 | | | fairly common in this district. |
| Cycloporus variegatus Kato, 1934 | Sep 1933 | | | single example found beneath a stone on the strand exposed to strong surf. |
| Prosthiostomum grande Stimpson, 1857 | May 1933 | | | three specimens of this species. |
| Stylochoplana clara Kato, 1937 | 1944 or earlier | | | Commonly found living on eel grasses, Zostera and Phyllospadix. |
| Planocera pellucida (Mertens, 1832) | 1944 or earlier | | | Off Susaki near Simoda, Izu (a single specimen). Holopelagic species. Very common in Pacific, Atlantic and Indian Oceans, between 42 degrees North and 54 degrees 42 minutes South. |
| Planocera multitentaculata Kato, 1940 | 1944 or earlier | | | Usually found together with Planocera reticulata. |
| Paraplanocera oligoglena (Schmarda, 1859) | 1944 or earlier | | | |
| Thysanozoon vulgaris Palombi, 1939 | 1944 or earlier | | | |
| Pseudoceros flavomarginatus Laidlaw, 1902 | 1944 or earlier | | | |
| Pseudoceros izuensis Kato, 1944 | 1944 or earlier | | | |
| Eurylepta susakiensis (Kato, 1934) | 1944 or earlier | 0-20 m | | from tidemarks to the depth of 20 m. |
| Cycloporus japonicus Kato, 1944 | 1944 or earlier | | | commonly found on compound ascidians. |
| Stylostomum maculatum Kato, 1944 | Jul 29, 1938 | | | A single specimen found on a certain white compound ascidian. |
| Leptoteredra tentaculata Kato, 1943 | 1944 or earlier | | | A single specimen found on a certain white compound ascidian. |