CYPRIDINELLA. 



21 



11. CYPRIDINELLA. Genus novum. 



The foregoing oval-oblong Ci/pridincB (Nos. 1 — 13) have rounded hind quarters, with 

 occasional evidences of a posterior spine ; and their antero-ventral margin is rarely produced 

 as far as the vertical line of the beak. Several recent analogues for the members of this 

 group have been pointed out above. We now have to treat of another group in which the 

 carapaces are not oblong ; they have always a more or less produced hinder margin, either 

 apiculate and indented, or spined at the postero-ventral margin of each valve ; and their 

 front margin is produced, often to a considerable extent, as a prow. Excepting that the 

 oval-oblong Cypridina Zelandica, Baird, and C. liiteola, Dana, have the lower front margin 

 rather more prominent than other known living forms, we are without a recent analogue 

 for these smooth, ovate, apiculate Cypridinm ; the long, sharp-tailed, recent forms, such 

 as C. Beynaudii, elongata, Bairdii, &c., having no chin-like projection under the notch. 



There is a closer alliance in form between the group under notice and the next two 

 groups than between it and the foregoing group of Cypridina proper. 



Judging, therefore, by the features of the carapace, which alone remains for our 

 examination, we determine to separate the group in question as a genus, imder the name 

 CypridinellAj knowing that the differences of the soft parts of the Cypridinads 

 are so great among the various forms as to be an additional basis of probability for a 

 real generic distinction. 



The following seven species are arranged according to the increasing projection of 

 the lower front margin. Cypridinella clausa and C. Maccoyiana are apiculate and 

 indented behind ; the others elliptically rounded, and probably once spined. 



1. Cypridinella Cummingii. Sp. nov. Plate II, figs. 23 a — c. 



Carapace-valves highly convex, broad-ovate, attenuated posteriorly, deeply notched at 

 the middle of the broad front. The carapace was egg-shaped, as thick as it was broad 

 (high). Edge-view long-ovate ; end-view broad-obvate. 



This is somewhat like the recent Cypridina Zelandica, Baird, in shape; but the 

 notch is too large, and the shell too convex and too narrow behind. 



Length height thickness ^ inch. Proportions 10 : 8 : 8. 



Of the ovate Cypridinadce, more or less distinctly apiculate behind, and produced to 



