157 



68. Cyprideis sorbyana (Jones). 



(PI. LXXII, fig. 2). 

 Cytheridea sorbyana, Jones, Monograph of Tertiary Entomostraca, p. 44, PI. IV, fig. 6. 



Syn: Cytheridea dentata, G. O. Sars. 

 ,, inermis, G. O. Sars. 



Specific Characters, Female. Shell rather tumid, seen laterally, short 

 subtriangular in shape much higher in front than behind, greatest height nearly 

 equalling 2 /a of the length, dorsal margin boldly arched in front of the middle 

 and sloping steeply behind, more slowly in front, ventral margin almost straight, 

 anterior extremity broadly rounded, posterior much narrower, tapering below 

 to an obtuse corner; seen dorsally, broadly oval in outline, with the greatest 

 width in the middle and about equalling the height, anterior extremity 

 bluntly pointed, posterior obtuse. Surface of shell slightly hairy and roughly 

 sculptured with concentric ridges and sattered tubercles, anterior edge of valves 

 armed with a row of about 7 denticles, less marked on the left valve; right 

 valve moreover provided, somewhat below the infero-posteal corner, with a 

 very conspicuous blunt spine pointing obliquely downwards, quite absent on 

 the left valve. Anterior antennae with the terminal part a little longer than 

 the distal*segment of the basal one, middle joint almost twice as long as the 

 1st. Posterior antennae with the flagellum comparatively feebly developed. 

 Vibratory plate of mandibular palp small, with only 4 setae. 



Colour of shell not yet ascertained. 



Length of adult female 0.90 mm. 



Remarks. The reference of this form to the genus Cyprideis would seem 

 to be somewhat questionable, as it differs conspicuously from the type described 

 above in the shape and sculpturing of the shell. Yet, I have thought it right 

 to place it provisionally in the present genus, as I have found otherwise some 

 evident accordances, thus in the peculiar armature of the right valve with a 

 very conspicuous toothlike process at the infero-posteal corner. My acquaint- 

 ance with the species was formerly confined to 2 detached valves only, a left 

 and a right, and the strongly marked dissimilarity of these valves led me to 

 the establishment of 2 spurious species, described under the names of Cythe- 

 ridea dentata and C. inermis. Brady, however, having had the opportunity of 

 examining a perfect shell, with both valves in situ, could ascertain the per- 

 plexing asymmetry of the valves in the present species, which he rightly iden- 

 tified with Cytheridea sorbyana described as early as the year 1856 by Jones 

 from fossil shells. 



