198 DE. G. S. BRADY ON NEW OR 



Family CYTIIERID.E. 



Genus CyxnERn: Miiller. 



Cytiiere sicula, sp. nov. (Plate XXV. figs. 1-7.) 



Shell of the male (fig. 1), seen from the side, elongated, subquadrangular, widest in front 

 of the middle, more tlian twice as long as broad ; anterior extremity broadly rounded, 

 posterior obliquely subtruncate, rounded off at the angles; dorsal margin sloping 

 steeply toward the front from the region of the hinge-tubercles, less steeply and with a 

 gentle curve backward ; ventral margin straight, with a slight sinuation anteriorly : 

 seen from above (fig. 2) elongate-ovate, fully twice as long as broad, tapering evenly 

 to the obtusely pointed extremities, greatest width in the middle, llight valve larger 

 than the left, which it overlaps considerably on the dorsal and posterior margins ; valve 

 of the left side much narrower, with no elevation over the hinge-tubercle and distinctly 

 excavated above the middle of its posterior margin. Valves fringed, except on the dorsal 

 and middle of the ventral margins, with closely-set, short hairs ; the marginal portions 

 of the valves, more especially at the two extremities, form a smooth encircling flange 

 which is marked radially by transverse lines prolonged from the bases of the fringing 

 hairs ; bordering the inner margin of the flange, the shell-surface is marked out into 

 polygonal areas (fig. 4), the interspaces being dotted with small closely-set impressions ; 

 beneath the dorsal margin at its anterior third is, on each valve, a very conspicuous 

 polished tubercle, partially surrounded by a smooth, non-punctate area. The shell of 

 the female is nearly as long as that of the male, but wider, and the lower half of the 

 posterior margin is prolonged into a wide angular beak (fig. 3). Length -88 mm. The 

 internal anatomy presents no characteristic features. The antennules, antennae, and 

 third pair of feet are here figured (figs. 5-7). 



Hah. In fresh water, Syracuse. Numerous specimens of both sexes. 



This species has many points of resemblance to Cythere lutea Miiller and C. ruhida 

 Erady ; but from the former it is separated by the more angular outline and the con- 

 spicuous marginal flange, from the latter by slight diversity of form as well as by its 

 greater size and more delicate sculpture ; both of these are, however, littoral marine 

 forms, whereas the recorded habitat of C. sicula is " fresh water." One can easily 

 imagine that differences such as characterise C. sicula may well have been produced by 

 change of environment in species like C. ruhida or C. lutea. 



