FAMILY 33. ROTALIIDAE 265 



Genus ELLIPSOLAGENA A. Silvestri, 1923 



Plate 38, figure 10 

 Genotype, by designation, Lagena ventricosa A. Silvestri 



Ellipsolagena A. Silvestri, Mem. Pont. Accad. Rom. Nuovi Lincei, ser. 



2, vol. 6, 1923, p. 265 (name only). 

 Lagena (part) of authors. 



Test monothalamous, with an internal tube at one side of the 

 chamber from the aperture which is elongate, subterminal, 

 curved, with one side raised into a protecting hood. 



Tertiary and Recent. 



This family for which a number of other generic names have 

 been proposed is peculiar in the distinct hooded form of the aper- 

 ture which in end view is usually semicircular. The internal 

 connecting tubular structure is closely similar to that of the 

 Buliminidae from which this family is derived, probably through 

 Virgulina. It developed in the Upper Cretaceous and is still 

 represented in the present ocean. The relationship to the 

 genera of the Lagenidae is not as close as the similarity of the 

 generic names would indicate. From the early biserial forms 

 which are near to Virgulina, the series of chambers becomes 

 either entirely involute as in EllipsohuUmina or continues on 

 into uniserial forms becoming entirely involute in Ellipsoidina 

 and finally in Ellipsolagefia single-chambered as an end form. 



FAMILY 33. ROTALIIDAE 



Test generally trochoid except m Spirillina, all the chambers 

 visible from the dorsal side except in a very few genera which 

 become partially involute, only those of the last-formed whorl 

 usually visible from the ventral side; wall calcareous, usually 

 rather coarsely perforate ; aperture typically on the ventral side 

 of the test. 



KEY TO THE GENERA 



I. Test consisting of proloculum and tubular coiled undivided second 

 chamber. 



A. Test planispiral Spirillina. 



B. Test trochoid. 



1. Ventral side open showing the earlier coils Tiirrispirillina. 



2. Ventral side with the chamber completely involute. 



Conicospirillma. 



