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end, posterior more obtuse and somewhat obliquely deflexed; seen dorsally, 

 broadly ovate in outline, with the greatest width quite behind and considerably 

 exceeding the height, anterior extremity gradually tapered to an obtuse point, 

 posterior broadly rounded off and somewhat emarginate in the middle. Valves 

 rather transparent, with the surface smooth and of a pearly lustre, but marked 

 with scattered small knobs. Eyes well developed; but no pigmentary spot in 

 front of them observable. Anterior antennae with the terminal part com- 

 paratively narrower than in the preceding species, none of the setae spiniform. 

 Posterior antennae differing from those in the said species except by the apical 

 claws being somewhat more slender; vesicle leading to the flagellum much 

 smaller. Last pair of legs with the 1st joint of the terminal part somewhat 

 longer than the other 2 combined. 



Male of somewhat smaller size than female and having the shell much 

 less tumid, seen dorsally, regularly oval in outline, with the greatest width in 

 the middle and the extremities almost equally contracted. Copulative appen- 

 dages with the terminal part triangular in shape. 



Colour of shell pearly white, transparent, with a somewhat ramified 

 reddish brown patch dorsally behind the ocular region; breading cavity of 

 female generally filled with numerous developing ova and embryos distinctly 

 traced through the pellucid shell. 



Length of adult female 0.64 mm. 



Remarks. The above-described form is easily recognised from the pre- 

 ceding one by the much more tumid shell, the posterior part of which is 

 distinctly depressed behind in the female; hence the specific name proposed. 

 It is also of rather larger size and much more transparent. 



Occurrence. I have taken this form not unfrequently in several places 

 on the Norwegian coast, from the Oslo Fjord to Lofoten, but only in some- 

 what greater deeps, in the Laminarian region. 



Distribution. British Isles, Spitzbergen, Greenland, Davis Strait, Gulf of 

 St. Lawrence, Bay of Biscay, Mediterranean, Kerguelen. 



Fossil. Norway, Scotland, Ireland, Holland, Canada, Calabria. 



Subfam. 8. Paradoxostominae. 



Remarks. This subfamily is here taken in a somewhat wider sense than 

 generally admitted, the genus Sclerochilus G. O. Sars, being included within 

 it, because I have found that this genus in some regards presents an evident 



