112 



the middle and about equal to the height, both extremities obtusely pointed 

 and nearly equal. Valves with the lateral faces evenly convex and all over 

 densely clothed with comparatively short but rather coarse hairs, anterior 

 margin of both valves armed with a row of about 8 coarse somewhat lanceo- 

 late denticles originating somewhat inside the edge; right valve moreover ex- 

 hibiting at the infero-posteal corner below 2 very conspicuous successive 

 denticles, the distal one rather long, spur-like. Armature of the valves in young 

 specimens rather dissimilar, the anterior extremity wanting the submarginal 

 denticles, but having the edge itself finely serrate, posterior corner of right 

 valve with a continuous row of coarse nearly equal denticles. Anterior 

 antennae with the basal part very massive, terminal part a little shorter, and 

 having the joints rapidly diminishing in size, the 1st being about as long as 

 the 2 succeeding ones combined. Posterior antennae with the penultimate 

 joint fully as long as the preceding joint, but much narrower, apical claws 

 slender and coarsely denticulated. Caudal rami exceedingly slender and narrow, 

 perfectly straight, with the apical claws very unequal in length, the distal one 

 being almost twice as long as the proximal one and about half the length of 

 the ramus. 



Colour dark green, in some cases with a brownish tinge, ovarial tubes 

 shining through the shell with a bright orange hue. 



Length of adult female amounting to 2.50 mm. 



Remarks. This form was recorded as early as the year 1776 by O. Fr. 

 Miiller under the above name, and has subsequently been observed by many 

 other authors, though some of them did not recognise it and described it 

 under other specific names, as seen from the above given list of synonyms. 

 It is one of our largest freshwater Ostracods, and may moreover be easily 

 recognised by its strongly vaulted and densely pubescent shell. The armature 

 of the valves is also highly characteristic. 



Occurrence. I have taken this form rather abundantly in small ponds 

 and swamps with grassy bottom, both around Christiania and in several other 

 localities of our country as far North as Tj0t0 on the Nordland coast, 

 spite of the heavy shell, the animal is well adapted for svimming, though 

 movements are not nearly so rapid as in most species of the next gem 

 Male specimens have never been met with of this species. 



Distribution. Throughout Europe, Siberia, North America. 



