Carapace tapers anteriorly, with clearly developed shoulder vaults. Ventral margin curves smoothly from below the incisure to a notch at about three quaners of the length where the right asymmetrical gland opens (C. macroprocera Habitus 1, C. macroprocera Habitus 3). Left asymmetrical gland opening ventral to the posterior end of the hinge adjacent to the postero-dorsal corner. Spines are absent from postero-dorsal corner (distinguishing this species from its siblings). Female carapace is more elongate than the male and has smoothly curved flanks, whereas in the male the flanks are slightly tri-convex.
Female, partially differentiated frontal organ almost three times the length of first antenna, capitulum region hirsute beneath, ends in a blunt point (C. macroprocera 1). The second antenna endopodite second podomere sparsely hairy (C. macroprocera 2).
Male, frontal organ stem equal in length to first antenna (C. macroprocera 3), capitulum down-turned with hairs arranged laterally in two lines and ventrally in a medial patch; first antenna "e" seta armature 28-30 pairs of long slightly curving spines (C. macroprocera 4).
Since this species was distinguished (Angel, 1971), it has been identified from several localities in the North Atlantic, but is yet to be found in other oceans. It is distinguished from its sibling species, C. procera (Conchoecia procera) and C. microprocera (the latter does not occur in our area), on the basis of its greater size, the lack of a spine at the postero-dorsal corner, the larger number of spines in the armature of the male first antennal "e" seta, and the slight hairiness of the second podomere of the female second antennal endopodite.
Presently known from 10°N-49°N in the North Atlantic. It is most abundant in equatorial waters, becoming very infrequent at higher latitudes. Bathymetric range shallow mesopelagic 100-400m.
Holotype, a male dissected and mounted on slides deposited in the British Museum (Natural History); BM(NH) 19126.96.36.199 (R.R.S. Discovery Map).
10°32.7'N 19°57.4'W; Discovery station 6665 haul 4; date 22nd February 1968, 1559-1731h; depth 400-295m; gear 1m2 ring net fitted with codend divider and with 0.32µm mesh.