490 MOLLUSCA. 
Figures 607, 607 a, front and lateral views of the animal and shell, 
enlarged. 
CLEopoRA PLACIDA (Gould). 
T. elongato-conica, vix reflexa: apertura circularis. Animal alis ob- 
longis obliquis, angustis, curtis, instructus. 
Alar expansions small, basal union narrow, oblong, the posterior 
margin nearly rectilinear, the anterior margin convexly arcuate, with 
a prominent spine at the middle, extremities slightly emarginate at 
each angle, so as to give a generally-rounded outline: basal lappet 
small, triangular, nearly equilateral, the apex reaching nearly to the 
separation of the wings. 
SHELL elongate, conical, recurved : aperture large and circular. 
Length about one-fourth of an inch; diameter of aperture about one- 
twentieth of an inch. 
Obtained in the equatorial Atlantic. 
Described from Mr. Dana’s uncoloured figure. 
The form of this shell seems to be more obtusely conical than in any 
other species, and the alar expansions are small. 
Figure 606, front view of the shell and animal, enlarged. 
Cieopora FALCcATA (Gould). 
T. elongato-conica, valdé recurva ; apertura circularis. Animal alis 
flabellatis, obliquis, subarcuatis, tridescentibus munitus. 
ANIMAL with the alar expansions large, flabellate, irregular, basal 
junction narrow, anterior margin undulately convex, somewhat emar- 
ginate beyond the spine, posterior margin deeply and undulately 
concave, one-half the leneth of the anterior edge, terminal margin 
