In Yamaguchi Prefecture, there are found Trishoplita eumenes eumenes and Trishoplita eumenes cretacea, which both belong to the "Trishoplita eumenes" complex. These two subspecies have four forms that were described by the differences in shell coloration. There are some opinions concerning the classification of this complex. In this study, the taxonomic relationship of these two subspecies is investigated based on various morphological characters of the hard parts and on habitat preference. As a result, the distribution areas of the two subspecies have been clearly separated. Both subspecies are arboreal, but Trishoplita eumenes eumenes lives on parts of trees that are up to 1 m in height from the ground, and in meadows. On the other hand, Trishoplita eumenes cretacea lives on trees at from 1 to 3 m from the ground, and in forests. It was revealed that significant differences were found in the t-test for the diameter of the shell, the height of the shell, the angle of the apex, and the thickness of the shell. Significant differences were also found in the Mann-Whitney test for height/diameter and diameter of the umbilicus/shell diameter. In addition, these two subspecies were distinguishable in coloration and the surface quality of the shells. These results strongly suggest that these two subspecies are distinct species. So we think Trishoplita eumenes eumenes and Trishoplita eumenes cretacea are two independent species.
A fossil pearl from the Upper Miocene Kubota Formation in the Higashitanagura area, Fukushima Prefecture, northeastern Japan is described. The pearl is spherical in shape and made up of layers of regularly foliated or crossed foliated structure composed of thin lamellar crystallites. It also contains a lenticular sublayer of prismatic structure composed of needle-like crystallites. These correspond to the shell microstructures of Crassostrea gigas, which occurs commonly in the same stratigraphic horizon, indicating that the pearl was formed by this bivalve species. The prismatic sublayer might have been formed as a result of abnormal secretion by the mantle epithelium of the mother shell.
Neilonella kuroshimaensis n. sp.スダレハトムギソデガイ（新種・新種） 殻長8.9 mm （ホロタイプ）。殻表は同心円状の肋があるところはキラハトムギソデガイに似ているが，殻頂は前から40％の所にあり，後部は嘴状に反り上がらない。また殻皮は同科の他種がオリーブ色であるが，本種はむしろ藁色。石垣島南方の黒島海丘の水深641 mから無人潜水探査機（ROV）ハイパードルフィンによって採集された。また，白鳳丸が奄美大島沖の水深576～594 mから採集した殻長3.1 mm以下の幼殻は本種と思われる。
The diel rhythm of glochidial release from gravid mussels of the species Pronodularia japanensis was investigated in the laboratory. Gravid mussels discharged glochidia principally at night, with a peak in the early part of the night. Glochidia formed a mass by entangling their larval threads.