RANDOM NOTES ON NATURAL HISTORY. 



15 



resembles it at all ; this is Strobila labyrin- 

 tliica, belonging to a different genus. They 

 are of the same shape but chersiua is the 

 larger of the two ; chersina is highly polished, 

 labyrinthiea is heavily striate ; labyrinthica 

 has a small umbilicus, chersina has none. 

 In chersina the lip is simple and sharp, 

 and the aperture open and free ; in looking 

 into the aperture of labyrinthica, a re- 

 markable peculiarity is seen, which will be 

 explained under that species. Its synonyms 

 are 



Helix chersina, Sa3s Gld., Ad., Reeve, 

 DeKay, Morse, Binney. 



Helix egena. Say, Chem., Rve., Pfr., 

 etc. 



Conulus chersina, Morse, Tryon. 



Many conchologists, both in Eui'ope and 

 America, have labored to prove this spe- 

 cies to be identical with Helix fulva, of 

 Europe. I think the}' must have studied 

 these two shells from poorly figured illus- 

 trations and ambiguous descriptions, for if 

 the}' had compared good specimens of the 

 two species together, the}' ought not to 

 have made so great a mistake. 



It is found everywhere in the United 

 States, east of the Rocky Mountains, under 

 leaves and on the under side of boards and 

 fence rails in moist places. I once found a 

 splendid specimen floating on a chip in 

 Mashapaug Pond. Say found his first spec- 

 imen in the Sea Islands of Georgia. Its 

 heighth and breadth are about one-tenth of 

 an inch. 



82. ZoNiTEs (Helicodiscus) lineata, Say. 



Syns : 



Planorbis parallelus, Say. 



Helix lineata. Say, Binn., Gld., Ad., 

 Fer., Desh., Chem., etc. 

 Helicodiscus lineata, Morse, Tryon. 



This unique shell was discovered by Say, 

 in upper Missouri, in company with a large 

 number of fluviatile species in a dried up 

 pond. The peculiar form of the shell, so 

 unlike any other land shell in America, to- 

 gether with the circumstance of finding it 

 in such a situation, led him to suppose it 

 was fresh water species, and he accord- 

 ingly described it as a planorbis. After- 

 wards, having found other specimens near 

 Philadelphia, under altogether diflferent 

 circumstances, he saw his error, and re- 

 described it as Helix lineata. 



It is not at all convex on the upper side, 

 like all the other species of this genus, but 

 is discoidal or planorboid shaped, that is, 

 round like a wheel, and flat. It has four 

 whorls, equally visible on both sides of the 

 shell and has a series of raised lines revolv- 

 ing on the body whorl. It has a decided 

 greenish color, is one eighth of an inch in 

 diameter, and is very common in Rhode 

 Island under leaves with chersina and 

 labyrinthica, etc. It is not very common 

 in the West, but quite so in New England, 

 along country roadsides. Its aperture is 

 narrow, semi-lunate ; lip thin ; within the 

 aperture on the outer lip, are situated two 

 small, conical, white teeth, and still farther 

 within the aperture can be seen another 

 pair of similar teeth, and in some speci- 

 mens, a third pair is seen by breaking 

 away a portion of the lip and whorl. The 

 shape of the shell, its raised revolving lines, 

 its green color, and the peculiar teeth 

 within the aperture, distinguish it from 

 any other species of shell known. 



83. ZoNiTEs (Striatura) milium, Morse. 



This is the smallest shell yet brought to 

 your notice ; its diameter is one-twentieth 

 of an inch. It was discovered by Mr. Ed- 

 ward S. Morse, in Maine, and described in 

 the P7'oc. Bost. Soc. Nat. Hist., vn., 28, 

 1859: 



"Shell depressed, transparent, shining, 

 white with a greenish tinge, marked with 

 distinct and regular striae of growth and 

 microscopic revolving lines ; whorls three, 

 rounded, rapidly increasing ; suture deeply 

 impressed ; lip simple and sharp ; aperture 

 very oblique ; umbilicus very wide and deep, 

 showing all the volutions." 



Thus far it has been found only in Maine, 

 Massachusetts, and Rhode Island. Very 

 little can be said of these smaller species ; 

 their habits cannot be studied very well, 

 and they are only to be found by diligent 

 search under the moist leaves of our thick, 

 hard wood forests. 



(To be cojitinued.) 



We desire to call attention to the collec- 

 tion of shells offered for sale on the last 

 page of this issue. They are exceptionally 

 perfect, of full size, and few collections of 

 its size contain so manv rarities. 



