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Brady and Norman, 1896

Marked sexual dimorphism in size (C. haddoni Habitus 1, C. haddoni Habitus 3). Female carapace large, strongly tapered with maximum height about three quarters the length. The postero-dorsal corner right-angled, lacking spines. The posterior margin curves smoothly into ventral margin. The male carapace is not so strongly tapered and is relatively broader (C. haddoni Habitus 2, C. haddoni Habitus 4). In both sexes left asymmetrical gland opening close to the postero-dorsal corner, and right asymmetrical gland at about a third height on posterior margin.
Female, frontal organ clearly differentiated, capitulum finely spinous almost all over (C. haddoni 1). First antenna, sensory setae short, less than half the length of the "e" seta. Second antenna endopodite (C. haddoni 2), second podomere carrying a "c" seta which is as long as the podomere - a feature typical of the bispinosa group (i.e., Claus' genus Orthoconchoecia).
Male, frontal organ capitulum down-turned, recurves anteriorly near tip (C. haddoni 3). First antenna "e" seta with double row of small stout spines becoming longer and thinner basally; 37- 42 spines in each row paired or arranged independently (C. haddoni 4). Second antenna endopodite with long "c" and "d" setae on the second podomere (C. haddoni 5).

A small race of this species occurs off Northwest Africa (females 2.15-2.5mm, males 1.75-2.0mm). The larger sensu stricto form seems to be restricted to waters where the production cycle is strongly pulsed seasonally. The smaller southern race may be a relict fauna from the period of the last glaciation 18,000bp and is now associated with the Northwest African upwelling region.

Reported from all oceans; 60°N-51°S in Atlantic, but large form seems to be bipolar with smaller races occurring at low latitudes. Typically mesopelagic in its bathymetric range. 1, 2, 3, 4 (R.R.S. Discovery Map).

Type specimens
Type material mounted dry on slide in British Museum (Natural History) so now useless for further taxonomic study.

Type locality
40 miles off Achill Head, Ireland.

Conchoecia haddoni