314 



LOWER INVERTEBRATES. 



into Charleston, S. C, by the French inhabitants for the purposes of food. The writer 

 several years ago, tried the experiment of introducing it into Xew England; but 

 although the places where specimens were distributed have since 

 been carefully searched, none have been found. It may be that 

 the east winds and the cold of winter prove too much for it. 

 Some if not all of our American species are edible ; JT. thyroides, 

 when treated with vinegar, has a very peculiar but pleasant taste, 

 excelling, in this respect. Helix albolahris. 



Another common species in the United States is Helix alter- 

 natd, in which the outer lip is sharp and the horn-colored shell is 

 ornannnted with blotches of dark brown. In New York and New 

 England it is even more common than // albohibris, occurring not 

 only in the woods, but in the open fields as well, although it seems 

 far more dependent on moisture than some of the other species. 

 It is not so palatable as H. thi/foules. Allied to H alteriiata is the 

 ,^~, pretty, but small species, H. asteriscns, in which 

 V 1^^ the whorls are ornamented by a number of trans- 

 w*A J verse ribs. It is only found in the northern states. 

 Fig. 371.— JJeiixasteris- Helix hurpa, which has a boreal distribution, is fi'=- ?r,a. — Helix 



ens '1 ■ • • atlirnata. 



found on both continents. The shell is high, and 

 oniameiited on the two lower whorls by transverse ribs. "The body is so translucent, 

 that, when extended, the ganglionic centres can be plainly seen. In motion it is ex- 

 ceedingly graceful, at times poising its beautiful shell high abo\-e its ^<5;-rt»-, 

 body, and twirling it around, not unlike a Phyisa, again hugging its 

 pretty harp close to its body ; the shell when in this last position, con- 

 tinually oscillates as if the animal [which is very small in proportion 

 to its shell] could not balance it ; it rarely ever moves in a straight 

 line but is always turning and whisking about, and this is done at 

 times very quickly and abruptly." 



In a large number of species like Helix 

 sai/i, dentifera, etc., a tooth is always dc- 

 velojjed on the columella, like that occa- 

 sionally found in Helix allMlabris, while in 

 another series, including tridentafa, palUata, etc., the aper- 

 tui-e is still farther contracted by the development of one or 

 more teeth from the inside of the outer lip. In one of this 

 latter group, H. hirsiUa, the aperture is \ er\' narrow, and the 

 outside of the shell is covered with numerdus short, stiff 

 hairs. 



The sjiecies of HulimiM are largely tropical, and tlie ma- 

 jority of the three hundred and odd species come from South 

 America. The animal is much like that of Helix, but the 

 shell is longer and has but a few whorls, while the lip is 

 thickened, reflected, and continuous with a callus layer on 

 the columella. Most of the species are large, some being 

 among the giants of the pulmonates, only exceeded by the 

 AcJiatincB to be mentioned in a moment. The largest species is Sidinms ovatus which 

 is common in the forests of southeastern Brazil ; the shell reaches a length of six inches. 





Tig. 31Z. — BuUmus. 



