The female resembles E. brittoni but differs from it by a more delicate appearance, the longer seta representing P5, and the comparatively narrow, serrate, hyaline flange on swimming leg spines. Farran's description and illustrations of O. exigua coincide so closely with two similar Arctic species that it was difficult to determine which species he had described.
Atlantic Ocean, Ireland NW, Norwegian Sea, Pacific NE, Arctic Basin, Mediterranean Sea
Exoskeleton thinly clerotized. Prosome about 1.4 times as long as urosome. Genital segment with areas external gonopores midway on anterior half of dorsal surface, each one with minute setule. Two short postgenital segments frequently telescopod partially or completely. Anal segment with operculum margin distended posteriorly. Caudal ramus with conspicuous expansion on dorsal surface, surrounding base of dorsal seta; dorsal seta nearly as long as inner and outer terminal setae, all resilient. P5 represented by 1 pedicellate seta on posterolateral corner of 1st urosomal segment which extends to ¼ of the genital segment; lateral seta on body near that corner. P6 probably represented by minute, blunt setule scarcely extending below genital operculum.
Prosome about 1.9 times as long as urosome. Anal segment and caudal ramus resembling that of female. Rostral area and mouthparts, except A1 and Mxp, as in female. A1 with armature similar to correspoding segments of female, except for absence of distal seta on 3rd segment. Mxp with 2nd segment expanded, with inner longitudinal cleft ; posterior expansion rimmed with several rows of setules. Swimming legs and P5 as in female, except endopod of P1 with terminal spine and distal seta modified. P6 probably represented by rounded posterolateral flap with hyaline corner on ventral surface of genital segment ; armature not discerned.