Stylochus erytheius sp. nov. (MNCN 4.01/3059 to 3113 and 4336 to 4535). Histological sections are antero-posteriorly oriented: A. Dorsal view of a living specimen; B. Ventral view; C. Detail of the tentacles and cerebral eyes; D. Histological section of the seminal vesicle; E. Histological section of the male and female copulatory organs; F. Sagittal reconstruction of the reproductive system. Abbreviations: cg, cemental glands; eg, extravesicular glands; ev, external vagina; fp, female pore; i, intestine; iv, internal vagina; ma, male atrium; mp, male pore; ov, oviduct; pp, penis papilla; pv, prostatic vesicle; sb, spermiducal bulbs; sv, seminal vesicle.