Adults and all 4 juvenile stages of the following marine freeliving nematode speeies be longing
to the superfamily Monhysteroidea are deseribed: Steineria elicia Gerlaeh 1956 from
Colombia, S.. pilosa (Cobb 1914) from Southern Chile, SubsphaelOlaimus litOlalis gen. n., sp.. n. from Southern Chile, Sphaelolaimus glacilis de Man 1876 from the eoast of the North Sea,
and Parasphaerolaimus parado.xus Ditlevsen 1918 from the Kattegatt.. All of them are eharacterized
by 8 groups of remarkable subcephalic setae.. The adult and the last two juvenile stages of another species of this group, Doliolaimus agilis Lorenzen 1966, are also described.
New diagnoses are given for the family Sphaerolaimidae and the genera Steineria,
Subsphaelolaimus, Sphaelolaimus, and Pamspaelolaimus.. Ineluded in the diagnoses is new
information on the presence and length ratio of the cephalic setae, on the structure of the
buecal cavity, and on postembryonic development.
It is notewortlry that (in the course during of the) postembryonic development three different
patterns can be distinguished as regards the sequence of appearence of the 8 groups of
subcephalic setae (cf chapter D) From the differences found between these patterns it is con-.
eluded that the diffCIentiation of the 8 groups is due to analogy and not to homology. This
analogy can be interpreted as a case of homoiology, since it is exelusively confined to the Monhysteroidea