Abstract
Two new lentic, relatively small-sized species of the gobiidid fish genus Rhinogobius, R. tyoni and R. telma, are described based on specimens from temperate regions of Japan. Rhinogobius tyoni (14 specimens, 25.7–40.0 mm SL) is distinguished from all congeneric species by the following combination of features: predorsal area with small cycloid scales; 8–17 predorsal scales; 20–23 pectoral-fin rays; 28–35 longitudinal scales; 10+16=26 vertebrae; a low first dorsal fin in males, not extending posteriorly to origin of second dorsal fin when adpressed; third spine of first dorsal fin longest; posterior oculoscapular canal usually absent; preopercular canal usually present; anteriorpart of first dorsal fin with no dark large circle or quadrangle markings; caudal fin with some dark vertical lines in males, some dark vertical lines or rows of dots in females. Rhinogobius telma (14 specimens, 28.7–39.5 mm SL) differs from all congeneric species by the following combination of features: predorsal area with small cycloid scales; 3–15 predorsal scales; 10+16=26 vertebrae; a low first dorsal fin in males, not extending posteriorly to origin of second dorsal fin when adpressed; third spine of first dorsal fin longest; lateral and ventral sides of belly with ctenoid and small cycloid scales, respectively; posterior oculoscapular canal and preopercular canal absent; first dorsal fin with a single longitudinal row of vertically-elongate dark markings; caudal fin with some vertical rows of dark dots in both sexes.
