A total of 11 polydorid species of the family Spionidae were extracted from non-calcareous substrata from Japan. The polydorids were: one Polydora sp., Polydora cornuta; three Dipolydora spp., Dipolydora quadrilobata, D. cardalia, D. socialis; one Carazziella sp., Carazziella spongilla; one Boccardiella sp., Boccardiella hamata; two Boccardia spp., Boccardia perata, B. proboscidea; three Pseudopolydora spp., Pseudopolydora cf. kempi, P. antennata, P. paucibranchiata. All inhabited mud deposits including mud in crevices of calcareous substrata, sponge and sandstone rocks, and were never found in self-excavated burrows in calcareous substrata. This study attempts to summarize and discuss the taxonomic, morphological, and behavioural characteristics of these non-boring species inhabiting Japanese waters and to compare them with the previously known boring species. The 11 non-boring species belonged to six genera. Thus their taxonomic and morphological variability was higher than those of boring species, which belonged only to three genera. A generic overview suggests that some genera contain many species capable of boring and others contain many species incapable of boring. Branchial blood vessels were thick and conspicuous in non-boring species. Moreover, they showed high crawling activity and a strong, vigorous palp movement. These observations suggest a possible link between boring activity and the morphology and behaviour in polydorids. In addition, Polydora cornuta, Dipolydora quadrilobata, D. cardalia, D. socialis, Boccardia perata and Pseudopolydora cf. kempi are new to Japan.