Spinoncaea ivlevi (Shmeleva, 1966), female, elongate form, general (northwestern equatorial Pacific) A urosome, dorsal, caudal seta V on both sides missing; elongate form, aberrant (northeastern equatorial Pacific) B P4-bearing somite and urosome, ventral, showing ornamentation on P4 and P5-bearing somites and genital double-somite, ventrolateral lobes arrowed, caudal seta V on left side missing C P5-bearing somite and genital double-somite, lateral, showing 2 long setules on ventral side of double-somite, midventral spinous process and ventrolateral lobe arrowed. Spinoncaea ivlevi (Shmeleva, 1966), female, robust form, variation, (northwestern equatorial Pacific) D setular patch on tip of cephalosome, dorsal E setular patch on cephalosome, lateral. Scale bars in μm.