A new species and genus of nematodes (Ungellidae, Drilonematoidea) parasitic in the coelomic cavity of Notiodrilus bovei deposited in the collection of the Museum für Naturkunde in Berlin, is described and illustrated. Malvinia crassa gen. n., sp. n. is characterised by its short, bloated, curved body tapering to both ends, paired, superficially attached cephalic hooks, short infundibular stoma, a pharynx comprising a pre-corpal bulb-like swelling, procorpus, isthmus and basal bulb, nerve ring encircling isthmus, excretory pore located posterior to the nerve ring, weakly cuticularised excretory duct, vulva, slightly post-median, short precloacal process in males, large grain-like spermatids, sperm in spermatheca ball-shaped, ca 20 μm diam., composed of smaller particles resembling spermatids; symmetrically placed, large, fimbriate caudal organs lacking a cavity, and absence of amphids, cephalic and male cloacal sensilla and post-uterine sac. Malvinia gen. n. is differentiated from all genera of the Ungellinae on the basis of its small size, vesiculate vs vermiform body shape, very long reflexed portion of testis and highly modified sperm. From the closest species of the genus Ungella, the new species differs by the presence vs absence of a stoma and pre-corpal swelling of the pharynx, structure of fimbriate caudal organs, larger spermatids in male and sperm in female spermatheca, and absence of lateral differentiation of the cuticle. A key to the genera of Ungellinae is proposed.