86 



RANDOM NOTES ON NATURAL HISTORY. 



species is identical witli L. pahislris, Miil- 

 ler, a species which inhabits the whole of 

 Europe and Siberia. This is not m}- oi>in- 

 ion, but if they should be identical, its 

 name should be L. palustris, Miill, as that 

 species was described in 1774. 



L. elodes are found all over Rhode Island 

 • in slow and rapid streams, stagnant ponds, 

 or wherever there is an abundance of de- 

 caying vegetable matter. Very large speci- 

 mens may be obtained from a pond near the 

 railroad, just this side of tlie Lonsdale 

 station, while the most perfect ones are 

 found in the Providence and Worcester Canal 

 near Log Bridge, where they are very 

 abundant. The^' must be collected in June 

 to obtain them in their best condition, for 

 after that month only ^oung ones can be 

 found alive. They attain their full size and 

 age by the first of Juh', and at this time 

 they cluster together and begin to devour 

 each other's shells. The young mollusks 

 grow rapidlj- during the summer and fall, 

 and on the approach of winter bury them- 

 selves in the mud until the spring opens. 



125. LiMN.i;A (Limnophysa) Humilis, Say. 



There are eight or ten species of Limnaea 

 found in the United States, which have been 

 referred by different authors to the species, 

 making as man}'^ synonyms of it as their 

 opinions concerning it. As most of these 

 are probably distinct species, I will mention 

 only the one variety which is found in 

 Rhode Island, which differs from the tj'pical 

 species. 



Limnsea humilis, as Sa3' named it in 1822, 

 is a small, ovate-conic shell, of a light 

 olive, or sea-green color when clean, but as 

 found living, it is almost always covered 

 with a coating of mud. Those found in 

 this vicinity are easil_y cleaned, but the 

 western specimens, covered with the cal- 

 careous mud of that section, require a little 

 dilute chlorhydric or hydrochloric acid to re- 

 move the lime. The animal is of a bottle- 

 green color above, dotted with amber spots, 

 and paler beneath. Shell seven-twentieths of 

 an inch in length, with four or five whorls, 

 a little shouldered or flattened above ; body 

 whorl two-thirds the size of the shell ; aper- 

 ture a little more than half the length of 

 the shell, rounded ; inner lip reflected over 

 a small umbilicus. It is found on the 

 margins of muddy pools, especially in de- 



[)reshions in the earth fllled by rain or melt- 

 ing snow in spring, and dry during the 

 summer. On the cross road from Lonsdale 

 to the Diamond Hill Road, about half-way, 

 on the right hand side, under a tree close 

 to the road, is a good locality, where in 

 spring they can be found clinging to stones, 

 and in the summer in the dried mud. If 

 placed in a vessel of clean water they will 

 crawl out of the vessel and will live several 

 days out of the water, but if not replaced 

 bj' this time they will die, although they 

 live all summer after the pond has dried 

 up, by the side of stones, which condense 

 a little moisture from the atmosphere, even 

 in the dryest weather. 



The variety alluded to above, was called 

 LymniBa umbilicata by Professor Adams, 

 who described it in the Am. Jour. ScL, 

 XXXIX., 374, 1840. Some authors con- 

 sider it as a distinct species. W. G. Binne}' 

 in Land and Fresh Water Shells of North 

 America, Part II., p. 56, 1865, makes it a 

 synonym of L. caperata. Say. Several 

 years ago I visited a small pool at Paw- 

 tucket, called the " Fountain," a depres- 

 sion about twelve feet in diameter, perhaps 

 two or more feet deep, filled with water 

 most of the year. In summer there are 

 times when it is nearly dry, and on one of 

 these occasions I collected a few specimens 

 of what was then a new species to me. A 

 short time afterward I showed them to 

 Prof E. S. Morse, who pronounced them 

 L. umbilicata, Adams. Two years after, 

 having used most of m}' specimens for ex- 

 changes, I again visited the spot. To my 

 surprise not an umbilicata could be found, 

 but in their place were plenty of the typical 

 L. humilis, of which none were present on 

 m}' former visit. Unless the umbilicatas 

 were 3'oung or updeveloped humilis, in or- 

 der to explain this curious phenomena, we 

 must call in an act of special creation dur- 

 ing the period of two years, and the utter 

 extinction of the former species. 



Besides the genus Limnaea, containing 

 over two hundred species, of which five in- 

 habit Rhode Island, as above, there are 

 also eleven other genera in the sub-family 

 Limnaeinae, of which two are represented in 

 the United States. These are Physa, with 

 one hundred or more species, and Aplexa, 

 with twenty-five. We have two species of 

 Physa and one of Aplexa in Rhode Island. 



