The fishes of the family Hoplichthyidae were in a general state of confusion until Jordan and Thompson revised them in 1913. During the course of our study of the Japanese deep-sea fishes, however, some additional facts have been found that require us to present our different analysis. In order to clarify the status and relationship more satisfactorily comparative studies have been undertaken from a viewpoint of the biometry and anatomy. In the biometric study we applied four methods as shown in chapter 2. In the anatomical study all the skeletons and alimentary canal have been examined. The results are shown in chapter 3 and 4. Based upon our biometric and anatomical studies we considered the relationships of all the hitherto known species referable to the family Hoplichthyidae. The results are shown in chapter 5. In the present study we examined four species, Hoplichthys langsdorfii Cuvier and Valenciennes, H. gilberti Jordan and Richardson, H. filamentosus, n. sp.and H. fasciatus Matsubara from the Japane and its adjacent waters, which are called herein L. G, Fi and Fa respectively. Unfortunately no specimens of H. regani Jordan and Richardson have come under our examination.
In his elaborate work, Schultz (1938) has referred 7 species under the genus Polyipnus. Of these, 3 ones, P. spinosus Günther, P. asteroides Schultz and P. nuttingi Gilbert, are known to occur in the Japanese waters. Lately the writer examined 26 specimens which are referable to the present genus, taken from Kumano-Nada by deep-sea trawler and ascertained that they are represented by two distinct species, Polyipnus spinosus and P. asteroi-des. Upon careful examination of these specimens the writer has found the various important differences between them and pointed out the misidentifi-cations made by some Japanese ichthyologists. The differences of these two species may be understood in the following comparison (See also Figs. 2 to 6).