44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 'j'J 



bers visible from the dorsal side, only those of the last-formed coil 

 visible from the ventral side ; test composed of several coils, usually 

 three or four in the adult test ; chambers rather numerous ; aperture 

 a slit at the umbilical margin of the ventral side of the chamber. 



Genus CYMBALOPORA Hagenow, 1850 

 Plate 10, fig. 2 



Test free, early chambers spirally arranged, later ones annular or 

 irregular ; umbilicate ; v^all finely perforate ; chambers as added often 

 not contiguous, but separated from one another by some distance along 

 the periphery, marked on the ventral side by depressions radiating 

 from the central umbilicus ; in the various species the early chambers 

 following the proloculum are usually brownish in color, this being 

 wanting in the later adult chambers. 



Genus TRETOMPHALUS Moebius, 1880 

 Plate 10, fig. 3 



Test free, early stages D\scorhxs-\\V^, in a low conical spire ; last 

 formed chamber globular, larger than the entire early growth ; wall 

 perforate, the last formed chambers with very large ones ; aperture 

 in adult chamber rounded with an entosolenian neck. 



Genus PLANORBULINA d'Orbigny, 1826 



Plate II, fig. I 



Test typically adherent ; early chambers in a close coil, later cham- 

 bers surrounding the periphery in an annular arrangement ; chambers 

 in a single layer ; test attached by its dorsal side, noninvolute ; all 

 chambers usually visible from either dorsal or ventral side ; wall per- 

 forate, often rather coarsely so ; aperture in the early chambers single 

 on the inner border of the chamber in the coiled chambers, in those 

 arranged in an annular manner usually two, one at either end of the 

 chamber and near the preceding chambers adjacent and together 

 forming a series of apertures about the periphery of the test ; each 

 newly added chamber connects with the two adjacent chambers at 

 either side in the series next previously formed. 



Genus TRUNCATULINA d'Orbigny, 1826 

 Plate 9, fig. 5 



Test free or adherent, rotaliform, the ventral face usually the more 

 convex but passing into species which are nearly biconvex ; chambers 



