.MAKVLAND U1:(JL(JGR:AL .SL"li\i:Y 119 



Fnmilv CYTHHRIDAF. 



Ck-mis CYllll-.Kl-; Miillri. 

 CyTIIEUK ilAUVl-ANJJlCA 11. .sj). 



Plate XVT, Figs. 16-18. 



Dcsvripihin. — ('ar;i[iiUT alHuit 1 .() niin. in li'ii;^th aiid (»..").") mm. in 

 lu'i,i;Iit and lliickness, siilxivatr in oiillinc; liiiiii'c si raiiilit, liall' tlir en- 

 tiro len^Lilli <il' carapaee, Ncnlral (inllinc ln'oadly arcnatc: antci-im- end 

 obli([uely I'oundcd. most lu'dmincnt in liir lowci' iialf and mndi wider 

 llian tlu' posU'i'ior end; the latter is neatly I'onndi'd lielow, <ii)tnsidy angu- 

 lar alidve the nnddle, then straight or slightly sinuate to the suhangular 

 extremity of the hinge line. A^alves unequal, the left overlapping the 

 right, very convex and swollen in the middle and thickest near the 

 ventral edge. The swollen region of the valves is of subtriangular shape 

 and sharply deilned where it rises from the relatively small, compressed, 

 terminal remnants of the surface. Of these remnants the posterior is 

 more depressed (it may appear like a flattened border) and narrower than 

 the anterior one, and both are marked with shallow pits arranged in 

 rather obscure concentric series. The surface of the swollen region is 

 more distinctly pitted, with the pits arranged in the lower half between 

 more or less sharp longitudinal curved riblets and much less regularly 

 in the upper half. Sometimes the swelling is terminated below by one 

 or two ribs more prominent and stronger than the rest. Edge view 

 subovate, with the ends produced; end view^ subtriangular with the lat- 

 eral lines rather strongly convex. Hingement consists as nsual in 

 Cythere of large lateral teeth and connecting bar. 



This seems to be a well-marked species with not very close relations 

 to C. trigonula Jones and C. 'triangularis (Reuss) Jones. From both 

 it differs in outline, the former, varying further in, having also a finer 

 surface punctation, a much more triangular end view% and relatively 

 very slightly compressed ends causing the edge view to be equally dif- 

 ferent. C . triangularis agrees better in end and edge views but its sur- 

 face differs decidedly, being " smooth, shining, and beset with scattered 

 setae." Another of the species described by Jones in his Monograph of 

 the Tertiary Entomostraca of England, especially since he mentions 

 that he has a scarcelv distinguishable varietv of it from the middle Ter- 



