Carapace of female subrectangular with a slight anterior taper (C. hyalophyllum Habitus 1). The height about 50% of the length, the dorsal margin nearly straight, ventral margin slightly concave. Postero-dorsal corner a blunt right angle. Posterior margin curving abruptly into the ventral margin. Male carapace lateral aspect less tapered, the rostra straighter, shoulder vaults more developed (C. hyalophyllum Habitus 3). In both sexes, in ventral aspect, rostra taper, antero-ventral margins beneath the incisure bowed, carrying longitudinal striae (C. hyalophyllum Habitus 2, C. hyalophyllum Habitus 4). Left asymmetrical gland opening just anterior to posterior end of the hinge. Right asymmetrical gland opening at the postero-ventral corner with immediately dorsally 1-3 additional lateral gland cells.
Female, frontal organ stem extending just beyond first antenna, capitulum slightly down-turned, ending in a curved point. First antenna segmentation obscure, second podomere carrying a long plumose dorsal seta, "e" seta is almost three times longer than sensory setae (C. hyalophyllum 1).
Male, frontal organ capitulum finely spinose over basal half, ends in a point (C. hyalophyllum 3). First antenna, "a" seta nearly as long as the limb, "c" seta minute, the "b" and "d" setae only just shorter than "e" seta, "e" seta armature 24-25 pairs of squat spines which, basally, are succeeded by a further 26-27 alternating spines (C. hyalophyllum 4). Second antenna endopodite, "b" seta carrying tuft of long hairs at midpoint, right-hand hook appendage bent through two angles (C. hyalophyllum 5), lefthand bent through one.
This species distinguished from C. magna (Conchoecia magna) by the bowed anteroventral edges with longitudinal striae, the taper to the rostra in ventral aspect and the details of the male first antennal "e" seta. The male closely resembles C. parthenoda (Conchoecia parthenoda) but is distinguished by opening of left asymmetrical gland being adjacent to the postero-dorsal corner.
Recorded from all oceans. Extensive vertical migrant from mesopelagic depths to the bottom of the epipelagic zone at night. In the Atlantic it is known from 60°N-48°S. 1, 2, 3, 4 (R.R.S. Discovery Map).
None designated; status of original material uncertain.
Original material described from Northeast Atlantic off Orotava (Tenerife), 34°N 18°W, and also from the Mediterranean off Ischia.