(Iles, 1953)
Description
Small rather globose member of the rotundata group. Carapace height about 55-60% of the length, breadth about 45% in both sexes [C.teretivalvata-fem-lat; C.teretivalvata-male-lat]. The ventral margin curves smoothly from below incisure to the postero-dorsal corner. There is some anterior taper. Angle of postero-dorsal corner about 135°. In ventral aspect flanks smoothly curved, maximum breadth in females posterior of mid-length, in males at the mid-length [C.teretivalvata-fem-vent; C.teretivalvata-male-vent].
Female, frontal organ undifferentiated, capitulum region slightly enlarged, ventrally hirsute, ending in a blunt point [C.teretivalvata-1]. First antenna, dorsal seta absent, "a"-"d" setae about half length of "e" seta.
Male, frontal organ stem shorter than first antenna, capitulum, hirsute, swollen ventrally along basal two-thirds, terminally rounded [C.teretivalvata-3]. First antenna, the "a" seta minute, "b" and "d" setae subequal, slightly shorter than "e" seta, "e" armature 10 pairs of pointed spines which proximally become more spaced out [C.teretivalvata-4].
Size
Female 0.8-0.9 mm, male 0.9-0.8 mm carapace length.
Depth range
Generally, the species is shallow mesopelagic in its bathymetric range, but some adults undergo diel vertical migrations into the neuston at night.
Distribution in the North Sea
No information available.
World distribution
Recorded from the Atlantic and Pacific Oceans. In the Atlantic, it has been recorded from 60°N-29°S.
Remark
According to recent taxonomic revision, the species teretivalvata is placed in the genus Metaconchoecia (M.V. Angel, pers. com.). However, for technical reasons the former generic name Conchoecia had to be maintained in the multimedia files.
[After Angel, 2000]