380 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
The species belonging to this genus are : 
Hippomenella ( Mucronella ) perforata Maplestone, 1902. Recent, Australia. 
IHippomenella ( Lepralia ) peristomata Waters, 1899. Recent, Madeira. 
Hippomenella ( Lepralia ) mucronelliformis Waters, 1899. Recent. Madeira. 
Hippoponella Mppopus Smitt, 1867. A. Ordinary zooecia, magnified. B. Upper part of a 
zooeciuru, showing the aperture and two triangular hinge teeth. C. Zooecia with ovate avieu- 
laria. D. Zooecia and zooecia with sutural lines. E-H. Opercula. (A-G after Levinsen, 1916 ; 
H after Waters.) 
B '85 
Hippomenella ( Petralia ) convexa Canu, 1913. Lutetian. 
Hippomenella (Petralia) mucronata Canu, 1913. Lutetian. 
Hippomenella/ (Lepralia) semilevis Reuss, 1869. Priabonian. 
This genus, of which we describe 15 new- species, is a very natural one: the 
examination of our plates reveals no aberrant type. Un- 
fortunately, on account of an extraordinary polymor- 
phism, the determinations are exceedingly difficult, and 
the classification of these species has given us great 
trouble. 
A singular anomaly is the disappearance of the 
genus in the recent waters off Florida, where no species 
has been cited by Smitt in 1872, or by Osburn in 191-1. In 
Europe the genus made its first appearance in the Lute- 
tian in the vicinity of Bordeaux; it occurs fossil in the 
Priabonian, and it still exists at Madeira. It is correct 
to say that it is extremely rare, for only the type of 
Waters species exists in the Funchal Museum. 
This genus is intermediate between Ilippoporina 
Neviani, 1895, and Peristomella Levinsen, 1902 ; it con- 
tains some species which in their exterior aspect have exactly the appearance of 
species of the latter genus, but they are provided with cardelles. 
A '25 
Fig. 116 . — Genus Hippomen- 
ella Canu and Bassler, 1917. 
A, B. Hippomenella mucro- 
nelliformis Waters, 1898. A. 
Zooecium with its avicularia 
and areolae, X 25. B. Oper- 
culum, X 85. (A, B after 
Waters, 1898.) 
