RANDOM NOTES ON NATURAL HISTORY. 



71 



Family 42. ValvatidEe, contains one 

 genus, Valvata, Miiller, inhabiting ponds 

 and ditches and sluggish streams. There 

 are three sub-genera, two of which are 

 found in New England, each represented b}' 

 a single species. 



61. Valvata (Tropidina) tricarinata, 



Say. 

 Sy/is. : 



Cyclostoma tricarinata, Say, 1817. 



Valvata tricarinata, Say, Desh, Menke, 

 Hald., Gld., DeKay, Adams. 



Valvata carinata, Sowb. 



Valvata bicarinata. Lea. 



Valvata unicarinata, DeKa}'. 



Tropidina tricarinata, Chenu. 



Shell small, depressed, thin, nearly trans- 

 parent, of a greenish color ; whorls three 

 to four, flattened at the apex, and separated 

 by a canaliculate suture ; the whorls are 

 encircled by three keels ; umbilicus broad, 

 deep, and funnel shaped ; aperture circular, 

 lip simple ; breadth one-fifth inch. 



This is a ver}- curious species, and is sub- 

 ject to much variation in form, and in the 

 number of carina. The bicarinata of Lea, 

 having two keels, and the unicarinata of 

 DeKay, having but one, are referred to this 

 species. Professor Adams found in Ver- 

 mont specimens perfectly simple and round, 

 having no carina, to which he gave the 

 name of var simplex. Specimens are found 

 having all degrees of carination, showing 

 them all to be the same species. Say 

 found his specimens in the Delaware River 

 and afterward in the Missouri ; DeKa}' in 

 Lake Champlain and in the Erie Canal ; 

 Lea in the Schuylkill ; Adams in Vermont ; 

 Perkins saj's, 1870: " It is common in all 

 the ponds and streams around New Haven, 

 Conn." It has not been observed in Rhode 

 Island, but maj'^ 3'et be found here, as it has 

 a very extended range. 



Haldeman says of this species: "The 

 ova are deposited from the first day of 

 March to the end of Jul}', in transparent 

 masses, one-twentieth of an inch in diam- 

 eter, each containing a number of germs of 

 a bright green color, dotted with yellow. 



62. Valvata (Lyogyrus) pupoidea, 



Gould. 

 Shell small, imperforate, elongated-oval, 

 opaque, chestnut-colored when divested of 

 the rough, dirty pigment which usually cov- 



ers it ; whorls four to five, minutely wrinkled ; 

 apex obtuse ; the body whorl disjoined from 

 the preceding one ; aperture circular ; lip 

 simple, not touching the body whorl ; oper- 

 culum horny, concentric, apex central. 

 Length one-tenth inch, breadth tliree-for- 

 tieths. 



This shell was descril)ed in SilUtnan's 

 Journal, vol. xxxviii., page 196, 1840, by 

 Dr. A. A. Gould. It was first found at 

 Fresh Pond, Cambridge, Mass., on stones 

 and submerged sticks, and since then in 

 Canada, Maine, and Connecticut. On this 

 account I include it among Rhode Island 

 shells, as it has not yet been found here, 

 and I have never seen the shell, and know it 

 only by the description and figure in Gould's 

 Invert. Mass. 



Family 43. Palndinidse, contains three 

 genera of fresh water shells, which are con- 

 ical or globular in shape, with a thick olive- 

 green epidermis. Two of these genera are 

 represented in the United States, and one, 

 Paludina, Lam., in Rhode Island. The 

 genus Paludina contains about one hundred 

 species, divided among seven sub-genera, 

 three of which inhabit our country, viz. : 

 Paludina (restricted) or Vivipara, Melantho, 

 and Tulotoma. Our shell is the 



63. Paludina (Melantho) decisa, Say. 



It would be useless here to give the very 

 extended synonym}^ of this species. Mr. 

 Binney, in his Fresh Water Shells of North 

 America., gives the names of twenty syno- 

 nyms of this shell, five of which are certainly 

 distinct species. Our shell was described 

 under the name of Lymnaea decisa, by 

 Thomas Say, in 1817, in Nicholson's Ency. 

 In 1819 he changed the name to Paludina 

 decisa. This name was adopted by Gould,- 

 Haldeman, Adams, DeKay, Kuster, Reeve, 

 Binney, and others. In 1862 Mr. Wm. G. 

 Binney applied the name of Melantho decisa 

 to it, which name it has retained. 



So many descriptions have been given b}' 

 various authors to shells referred to this 

 species, that I can do no better than to 

 quote the original description by Say : 

 "Shell sub-conic, olivaceous, truncated at 

 the apex ; whorls four, wrinkled across, 

 entire ; within bluish white ; operculum cori- 

 aceous, elevated on the disc, and concen- 

 trically striated. Length one inch, breadth 

 three-quarters." It is found in ponds and 



