LIMACINID^. 95 



The pteropods are infrequent visitors to our coasts ; Spirialis 

 Flemingii, 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; the}" 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, thej^ 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 satisfactor}'^ 

 manner their sudden appearance and disappearance. They ci^eep 

 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 butterfl}^ to 

 propel itself forwards or upwards, the shell is carried at right- 

 angles, hanging somewhat obliquel}^ 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. 

 infiata, 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. S. clatJwata, Eyd. 

 (xlii, 23). 



PERACLE, Forbes, 1844. Shell oblong, not turriculated, spire 

 rather short, aperture prolonged into a long, curved canal. 2 

 sp. Eui-opean seas. S. physoides^ Forbes. 



Agadina, Gould, 1852. 



Distr. — A. cucicllata, Grid, (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 fioating near an iceberg in 60° 

 S. latitude and 106"^ 20' E. longitude. The animal is black, with 

 oval appendages, not lobed. 



