5 
Aplexa, Aplexus, and lastly Aplexia. 
36 Planorbis campanulatus 
Hartland, Vermont, rare. 
37 Planorbis bicarinatus 
Abundant, Hartland, Vermont. 
38 Planorbis exacutus 
Rare, Hartland, Vermont. 
39 Planorbis Lentus 
Rare, Hartland, Vermont. 
40 Planorbis parvus 
Diameter 5 mm; shell compressed, minutely striate, smooth, 
flat above, with center impressed; left side with a broad, shallow 
concavity; whorls 4, a great part of them, with the apex visible to 
the center, on both sides; sutures equally deep; aperture oval, 
oblique, longer than wide, peritreme undeviating; color light 
brown, sometimes with a greenish tinge. 
Hartland, Vermont, rare. Cantilles canyon, Baja California, 
on Chara, and other aquatic plants, abundant. Widely distrib- 
uted. 
41 Limnaea palustris 
Shell of moderate size, spire well elevated, whorls moderately 
inflated, subperforate, aperture somewhat narrowly auriculiform, 
columellar fold well developed; color variable from light to dark 
brown. 
Hartland, Vermont, common; Tracy cites a black form as rare. 
Widely distributed. 
42 lLimnaea desidiosa 
Hartland, Vermont, rare. West to Kansas. 
43 lLimnaea caperata 
Shell suboval, a little oblong, obscurely yellowish horn color; 
spire half as long as mouth; apex acute; whorls slightly wrinkled 
across, and with very numerous, equal, subequidistant, elevated, 
minute, revolving lines; suture not very deeply impressed; aper- 
ture rather dilated; lip fold not profound. 
Hartland, Vermont, rare. Hudson’s bay, south to New York; 
Michigan; Idaho; Utah. 
44 Ancylus parallelus 
Hartland, Vermont, rare. 
45 Valvata tricarinata 
Abundant in the Connecticut river, Hartland, Vermont. Wis- 
consin. 
46 Melantho decisa 
Windsor Co., Vermont, common. 
47 Amnicola limosa Say 
Hartland, Vermont, abundant. Utah. 
48 Carychium exiguum 
Oval-elongate, white, translucent, shining; spire long, apex 
