214 



Distribution. British Isles, Holland, Spitzbergen, Dawis Strait, Gulf of 

 St. Lawrence. 



Fossil: Norway, British Isles, Canada. 



110. Cytherura fulva, Brady & Robertson. 



(PI. XCIX, fig. 1). 



Cytherura fulva, Brady & Robertson, Ann. Mag. Nat. Hist., ser. IV, Vol. XIII, p. 116, 



PI. IV, figs. 15. 



Specific Characters. Female. Shell very tumid, seen laterally, suboval in 

 shape, equally high in front and behind, greatest height about half the length, 

 dorsal margin nearly straight in the middle and evenly bent both in front and 

 behind, ventral margin very slightly sinuated and gently boved behind, anterior 

 extremity well rounded, posterior produced in the middle to a rather short and 

 blunt protuberance; seen dorsally, broadly and regularly ovoid in outline, with 

 the greatest width somewhat behind the middle and considerably exceeding 

 half the length, side-edges quite evenly curved throughout, posterior extremity 

 more sharply pointed than the anterior. Valves nearly equal and rather 

 opacous, surface evenly convex and marked with scattered rounded tubercles, 

 exhibiting moreover a very delicate regular reticulation; inner duplicatures 

 much narrower than in the other known species and quite simple, being evenly 

 emarginated both in front and behind. Anterior antennae very slender, with 

 the last joint of the terminal part much prolonged, being almost twice as long 

 as the preceding joint. Posterior antennae with the penultimate joint extremely 

 narrow and wanting the usual dividing suture, the 2 lateral setiferous ledges 

 quite opposite. Mandibles with the outermost cutting tooth remarkably strong 

 and prominent, the others short and blunt. Maxillae with the distal joint of 

 the palp unusually prolonged. Legs of moderate length, last pair with the 

 1st joint of the terminal part about as long as the other 2 combined. 



Male of smaller size than female, but resembling it in the general shape 

 of the shell. 1st pair of legs comparatively more strongly built than in female. 

 Copulative appendages very large and compact, with numerous irregular 

 chitinous thickenings partly projecting anteriorly, copulatory string of very 

 delicate structure; terminal part not clearly defined from the basal one, and 

 ending in a thin triangular lamella. 



Colour of shell, according to Brady yellowish. 



Length of adult female 0.50 mm. 



