136 



or somewhat rhomboid in outline, the lateral edges being abruptly curved in 

 the middle, greatest width exceeding somewhat the height, both extremities 

 obtusely pointed, the anterior narrower than the posterior. Surface of shell 

 rather densely hairy, and distinctly sculptured with closely set small impressed 

 pits. Natatory setae on posterior antennae densely ciliated and extending beyond 

 the tips of the apical claws. Vibratory plate of maxillipeds provided with 5 

 setae. Caudal rami very small, lash-shaped, with a minute bristle on the dorsal 

 edge, terminal flagellum longer than the stem. 



Colour yellowish white, with 3 dark, somewhat irregular, band-like patches 

 running down the valves from the dorsal face to about their middle, the fore- 

 most patch lying immediately inside the anterior edge, the other 2 connected 

 dorsally on each side by a longitudinal band. 



Length of adult female 0.70 mm. 



Male unknown. 



Remarks. This form was described and figured as early as the year 

 1785 by O. Fr. Muller, and has generally been recorded by recent authors 

 under the name Cypridopsis vidua. It is the type of the genus Pionocypris, 

 as here defined. 



Occurrence. \ have taken this little Ostracod in many places of our 

 country in ponds and ditches with clear water and grassy bottom. Though 

 in most cases keeping at the ground, the animals are very well adapted for 

 swimming, and are seen at times moving rather quickly through the water. 



Distributions. Throughout Europe, Central Asia, North America. 



56. Pionocypris helvetica (Kaufmann). 

 (PI. LXIV, fig. 1). 



Cypridopsis helvetica, Kaufmann, Cypriden und Darwinoliden der Schweitz, p. 363, 

 PI. 19, figs, 4, 5; PI. 22, figs. 10, 11. 



Specific Characters. Female. Shell, seen laterally, of a shape rather 

 similar to that of the preceding species, though comparatively somewhat less 

 high in proportion to the length; seen dorsally, however, far less broad, and 

 regularly ovoid in outline, with the lateral edges quite evenly curved, and the 

 greatest width scarcely exceeding the height, anterior extremity narrower than 

 the posterior, which is rounded off at the end. Surface of shell quite smooth 

 and finely hairy, without any trace of the impessed pits characterising the 

 shell of the preceding species. Natatory setae on the posterior antennae still 

 more prolonged. Vibratory plate of maxillipeds with only 3 setae. Caudal 

 rami with the terminal flagellum very long and slender. 



