PTEROPODA. 487 
HYyAL@A INERMIS (Gould). 
T. ovato-globosa, postice angustata, compressa et truncata, angulis pos- 
ticis emarginatis, antice rotunda: apertura angusta, transversa, labro 
haud porrecto. Animal alis transversis angustis ad angulum posti- 
cum emarginatis instructus. 
ANIMAL, with the alar expansions flabellate, twice as Jong as their 
greatest breadth, convexly arched in front, anterior angle rounded, 
the ends with a deep slit at their anterior third, the posterior angle 
deeply and concavely emarginate; mantle oblong, with rounded _pos- 
terior angles, extending on the back of the shell about one-fourth its 
length ; interior mass heart-shaped, dusky. 
SHELL ovate-globose, with both valves very gibbous, the smaller 
one most so; line of union flexuous; mouth narrow, lip simple, not 
projecting over the opposite valve ; anterior end rounded, lateral lines 
somewhat converging ; the posterior angles concavely emarginate, the 
anterior angle of the emargination slightly spinous: posterior extre- 
mity compressed, truncate, the outline very slightly convex. 
Length seven-eighths of an inch; greatest breadth four-fifths of an 
inch; thickness equal to the breadth. 
Described from a figure by Mr. Dana; locality not mentioned. 
Figure 604, shell, with the animal; 604, 604 a, lateral and ventral 
views of the shell. 
HYyAL@A remorata (Gould). 
T. subcordata ; angulis posticis productis, arcuatis et cornua subrecta, 
prelonga, retroversa, gerentibus. Animal alis transversis trapezor- 
dalibus munitus. 
Alar expansions transverse, rather longer than broad, the anterior 
and posterior margins nearly parallel, but slightly arcuate convexly, 
