LIMACINID. 95 
The pteropods are infrequent visitors to our coasts; Spirialis 
Flemingti, however, occurred at Nahant, Mass., in great abun- 
dance during the summer of 1863. Mr. Alexander Agassiz gives 
the following account of its habits : 
They come to the surface of the water about an hour after 
dusk; they do not remain long, and after ten o’clock at night 
were rarely met with. He succeeded only once in finding a few 
isolated specimens during the heat of the day; while at full tide, 
soon after dark, they were very often found in abundance. These 
animals are very easily kept in captivity, and their habits, which 
can then be carefully watched, may explain in a very satisfactory 
manner their sudden appearance and disappearance. They creep 
about by means of their wing-like appendages. They but rarely 
left the bottom during the day, merely rising a few inches, and 
then falling down again to the bottom of the jar. After dark, 
however, they could all be seen in great activity, moving near 
the surface of the water as fast as their appendages enabled 
them. During the day, they often remain suspended for hours 
in the water, simply by spreading their wing-like appendages, 
and then suddenly drop to the bottom on folding them. When 
the animal is in motion, beating the water like a butterfly to 
propel itself forwards or upwards, the shell is carried at right- 
angles, hanging somewhat obliquely to the direction of the 
movement.— Bost. Proc., x, 14. 
HELICONOIDES, d’Orb., 1839. (Protomedea, Costa, 1861. Em- 
bolus, Jeffreys, 1869.) Shell thin, transparent, discoidal, sinistral, 
axis umbilicated ; whorls smooth; peristome disunited, notched 
on each side, and with an elongated, arched beak in front.  S. 
inflata, d’Orb. (xlii, 22). 
EuROMUS, H. and A. Ad., 1858. Shell oblong, not turreted, 
cancellated ; spire short, obtuse, last whorl swollen, much larger 
than the others; aperture large, elongate. . clathrata, Eyd. 
(xlii, 23). 
PERACLE, Forbes, 1844. Shell oblong, not turriculated, spire 
rather short, aperture prolonged into a long, curved canal. 2 
sp. European seas. S&S. physoides, Forbes. 
AGADINA, Gould, 1852. 
Distr.—A. cucullata, Gld. (xlii, 24). 
Shell colorless, pellucid, planorbular, one side showing five or 
six whorls, the other a single volution with a large umbilical pit; 
aperture oblique, campanulate, and projecting beyond the last 
whorl like a hood. 
The single species was found floating near an iceberg in 60° 
S. latitude and 106° 20’ E. longitude. The animal is black, with 
oval appendages, not lobed. 
