CYTHERELLA. 79 



22. Cytherella subrkniformis. Sp. nov. Plate VI, figs. 18 a — c. 



These suboval, smooth carapace-valves are strikingly like the specimens figured by 

 the late M. J. Bosquet, of Maastricht, from the Chalk of Holland and Belgium, first 

 (1847) as C. reniformis, and subsequently (1854) as C. ovata (Roemer). The American 

 specimens differ, however, in their less reniform shape and their more central convexity ; the 

 profile being lanceolate instead of narrow-ovate. Were these two sets of specimens found 

 together, instead of being widely apart, both geologically and geographically, we should 

 be inclined to regard them as varieties of one species ; as it is, we prefer to make the 

 most of their differences, and to call our figured specimens from Iowa C. subreniformis, 

 having reference to the fact that the Cytherella above-mentioned, referred to C. ovata by 

 M. Bosquet in 1854, was at first (in 1847) named by him C. reniformis, and being of 

 opinion that it is far better to keep it distinct (as C. reniformis, Bosq.) from C. ovata 

 (Roemer), with which it does not really agree. 



Length 1*4; height '64; thickness *48 mm. Proportions 26 : 16 : 12. 



C. subreniformis is from the Fusulina-limestone of Iowa, and is in Mr. J. Young's 

 collection. 



23. Cytherella concinna? (page 71). Plate VI, figs. 19 a, b. 



Two carapace- valves (one imperfect), long-oval, almost truly elliptical (as far as the 

 best, fig. 19 a, shows), occurred with figs. 18 a — c in the Carboniferous Limestone 

 (Pusulina) of Iowa. It is hazardous to give this form a specific name without a better 

 set of characters ; but it is comparable with C. concinna, figs. 9 and 12. 



Length 1*28; height -64; thickness ? mm. Proportions 32 : 16 : ?. 



24. Cytherella impressa. Sp. nov. Plate VII, figs. 8 a, 5. 



Carapace subelliptical, faintly curved on the dorsal and ventral margins ; round in 

 front, subangular behind ; smooth. Profile cuneiform, sharp anteriorly, thick posteriorly, 

 and indented on each side by the deep muscle-spot. 



Length '92; height '48; thickness ? mm. Proportions 23 : 12 : ?. 



This differs from the other Iowa specimens, and approaches in form some of the small 

 Scotch varieties of C. Benniei, but its posterior margin is too angular for any of them. 



This is from the Eusulina-limestone of Iowa, and is in Mr. John Young's collection. 



