Figure 4 from: Renaud CB, Naseka AM (2015) Redescription of the Far Eastern brook lamprey Lethenteron reissneri (Dybowski, 1869) (Petromyzontidae). ZooKeys 506: 75-93. https://doi.org/10.3897/zookeys.506.9817

Figure 4 - Oral disc of lampreys identified by Berg (1931) as Lethenteron reissneri without row of posterials. A ZIN 14457, Shangshi River, Songhua (Sungari) River system, People's Republic of China, 146 mm TL with complete posterial row comprising 24 unicuspid teeth (Pr1; only few of these teeth visible in photo). Note second row of posterials (Pr2). Two exolateral teeth additionally present on left side, one between first and second (E1) and other between second and third endolaterals (E2) B ZIN 15078 (re-identified as Lethenteron camtschaticum), Samarga River, near Sufren Cape, Russia, 178.0+ mm TL with complete posterial row comprising 18 unicuspid, 3 bicuspid, 1 unicuspid teeth (only few of these teeth visible in photo). Exolateral tooth present on right side between first and second endolaterals not visible because oral disc not fully open