A–C Internal anatomy of Rhiostoma housei specimen CUMZ 3982 from Tham Sriwilai, Saraburi, A inside view of lung cavity shows an arrangement of the kidney, circulatory system and the terminal part of the digestive tract B male genitalia and C female genitalia D spermatophore of Rhiostoma samuiense specimen CUMZ 4713 from Kanchanadit, Surat Thani with its cross sections showing spermatophore shape in each position. Abbreviations: an, anus; bc, bursa copulatrix; fc, faeces; go, genital opening; h, heart; kd, kidney; mc, mantle collar; od, oviduct; pg, prostate gland; re, rectum; sr, seminal receptacle; ut, uterus; v, vein; vd, vas deferens.