14 



RANDOM NOTES ON NATURAL HISTORY. 



Tne Shell-Bearing Mollusca of Rhode 

 Island. 



BY HORACE F. CARPENTER. 



Chapter XXV. 



79. ZoNiTES (Hyalinia) electrina, Gould. 

 This little shell was first found hy Mr. T. 

 J. Whittemore, on the borders of Fresh 

 Pond, in Cambridge, Mass., and was de- 

 scribed b}' Dr. A. A. Gould, in the Jour. 

 Bost. ISoc. Nat. Hist., in., 1840, under the 

 name of Helix electrina, viz. : "Shell small, 

 depressed, pellucid, fragile, amber colored ; 

 whorls four, conspicuouslj^ wrinkled b}- the 

 lines of growth ; aperture rounded ; lip 

 simple ; umbilicated." 



The shell is 7iot amber colored, as in 

 Gould's description, but smoky horn color, 

 and when the animal is living in it, the shell 

 appears almost black. The three species, 

 arborea, electrina, and indentata, can hardly 

 be distinguished apart b}^ a beginner in 

 the science. At first, when collecting these 

 species, I could never identify them, until, 

 arriving at home, I could compare them 

 with typical specimens. Bj- a close exam- 

 ination of full grown specimens of the three 

 species together, the following ditferences 

 will be noticed : electrina has three and one- 

 half whorls, indentata has four, and arborea 

 has four and one-half to five. In arborea, 

 the whorls increase slowl}- and regularly ; 

 in electrina, the last, or bod}' whorl, en- 

 larges rapidl}' in size, in which respect it re- 

 sembles indentata ; but the most apparent 

 difference between arborea and electrina is 

 in the color of the shell as well as of the 

 animal, and its more shining appearance ; its 

 umbilicus too, is a little smaller and its hab- 

 itat is unhke either of the others, being 

 found only in very moist places, under 

 leaves, in fact, preferring low, swampy 

 ground. The differences between this spe- 

 cies and indentata will be given under the 

 description of indentata. 



It is found everywhere in the United 

 States, east of the Mississippi River. F. A. 

 Sampson quotes it from Pettis Co., Missouri, 

 in the Bulletin of the Sedalia Nat. Hist. 

 Soc, Augu>t, 1885. Binney refers this 

 species to Helix viridula, Menke, thus 

 making it an European as well as an 

 American shell. Man}' conchologists are 



of this opinion, and the shell is called viri- 

 dula full as often as it is electrina. Helix 

 viridula, Menke, is one of the synonyms of 

 Zonites radiatulus. Reeve, and as I have 

 carefull}' examined and compared our shells 

 with the English radiatulus, I am satisfied 

 that the}' are not identical, and that elec- 

 trina, Gld. is its proper specific name. 



80. ZoNiTES (Hyalinia) indentata. Say, 

 This species was discovered b}- Say, and 



described in June, 1822, in the Jour. Ac. 

 Sci. Phila., 11., 372: "Shell depressed, 

 pellucid, highly polished; whorls four, with 

 regu'ar distinct impressed lines across, of 

 which there are about twent3'-eight to the 

 bod}' whorl, all extending to the base ; aper- 

 ture rather large ; lip simple ; umbilicus 

 none, but the umbilical region is deeply in- 

 dented." It inhabits the same range with 

 arborea, and is found in company with it, 

 under decaying leaves and also under 

 stones. It is about the same size as arbo- 

 rea, but is distinguished from it by being 

 lighter in color, in being polished, in having 

 one whorl less, and in the rapid enlarge- 

 ment of the body whorl. It is distinguished 

 from electrina by the absence of an umbili- 

 cus, by the color (indentata being whitish 

 and sometimes tinged with pink, while elec- 

 trina is smoky), and by the lines being 

 remote, while they are crowded in the other 

 species ; and from all other shells of this 

 genus, by the microscopic impressed lines 

 radiating from the umbilical dent, which 

 resemble water lines, or the lines on a 

 gooseberry, while the interstices are perfect- 

 ly smooth. 



81. Zonites (Conulus) chersina, Say. 



We have here a shell, very different in 

 shape from those heretofore described in 

 these pages ; instead of having, like them, 

 the apex slightly raised above the body of 

 the shell, we have one in which the thick- 

 ness, or distance from the apex to the base, 

 will measure as much as the diameter. It 

 is round like a top, with the spire elevated 

 like a cone. It was described bv Say, in 

 the Jour. Ac. Sci. Phila., 182r: "Shell 

 sub-globose, conic, pale yellowish-white, 

 pellucid, convex beneath ; volutions six ; 

 suture moderate ;labrum simple ; umblicus 

 none." 



It cannot be mistaken for any other Rhode 

 Island shell as there is only one other that 



