from, the River Scheldt and the Grecian ArcMpelago. 47 



line ; but the differences seem to be too slight to warrant se- 

 paration as a distinct species. One of these specimens is 

 %m-ed in PL YIII. tigs. 9, 10. 



Pontocypris obtusata^ nov. Sf). (PI. VIII. figs. 7, 8.) 



Carapace, as seen from the side, elongate, reniform, highest in 

 the middle ; greatest height considerably less than half the 

 length ,• extremities rounded : superior margin well arched ; 

 inferior sinuated in the middle. Seen from above, the outline 

 is compressed, ovate ; greatest width in the middle and 

 scarcely equal to one-third of the length, pointed in front, 

 nan'owly rounded behind. Shell-surface smooth. Colour 

 whitish. Length -^ inch. 



Cythere porcellanea^ nov. sp. (PI. VII. figs. 1-4.) 



Valves, as seen from the side, subclavate, higher in front than 

 behind ; greatest height in front of the middle, and equal to 

 half the length ; anterior extremity broadly rounded, poste- 

 rior obliquely rounded or subti-uncate : superior margin 

 boldly arched in front of the middle, thence sloping back- 

 wards with a slight concave curve, and ending abruptly in 

 an obtuse angle ; inferior gently sinuated. Outline, as seen 

 from above, ovate, equally pointed at the extremities, widest 

 in the middle ; width much less than the height. Shell- 

 surface smooth, each valve bearing an elongated mamilli- 

 form protuberance behind the middle of the ventral surface. 

 Colour yellowish white. Length J5 inch. 



One specimen only of this species was found. Though 

 approaching in shape C. casfanea, it is very different in general 

 appearance ; the smooth unsculptured shell and lateral protu- 

 berances are perhaps its best diagnostic marks. 



Cythere Jiiscata, nov. sp. (PI. VII. figs. 5-8.) 



Carapace, as seen from the side, oblong, subreniform , rather higher 

 in front than behind; greatest height equal to half the length ; 

 anterior extremity rounded, posterior slightly eraarginate 

 above the middle : superior margin almost straight, inferior 

 sinuated in the middle. Seen fi'om above, the outline is ob- 

 long ovate, acutely pointed in front, subtruncate behind; 

 greatest width less than the height, situated behind the 

 middle. Surface of the valves closely punctate. Colour 

 yellowish brown. Length V^ inch. 



Cythere affinis^ nov. sp. (PI. VII. figs. 13, 14.) 



Carapace compressed, oblong. Seen from the side, subreniform, 

 nearly equal in height tliroughout; greatest height less tiian 



