The morphological and taxonomic account of a new and the first terrestrial species of the largely marine genus Trissonchulus
Cobb, 1920 is given, along with descriptions of two known species of the sister taxon Ironus Bastian, 1865, reported for
the first time from India. Trissonchulus baldwini sp. n. is characterised by the lip region markedly offset from adjoining body by a
deep groove; lips strongly amalgamated forming a band or collarette; inner margins of lips serrated; small, setose and backwardly
directed cephalic sensilla; narrow funnel-shaped amphids; inconspicuous excretory pore; larger stoma with two dorsal and two
ventral outwardly curved, reversible teeth at anterior margins; expanded part 65-70% of the corresponding pharyngeal length; anterior
vulva (38-39%); reduced anterior genital branch; long filiform tail and absence of males. The species Trissonchulus lichenii
Nasira et Turpeenniemi, 2002 has been placed under genus Syringolaimus de Man, 1888 as S. lichenii on the basis of affinities with
the latter. The population of Ironus dentifurcatus Argo et Heyns, 1972 shows slight variations from the original population in having
narrower amphids, fang-like projections of the dorsal tooth, conspicuous crystalloids and the presence of caudal pores, while
the population of I. terranovus Ebsary, 1985 shows variations from the original specimens in having a smaller body, dome-shaped
head and a pair of caudal pores. On morphological grounds, among the congeners T. baldwini sp. n. has been found to show a
close relationship with T. acutus and T. benepapillosus while showing many affinities to I. terranovus and I. dentifurcatus on account
of morphometric characteristics.