THE : CONCHOLOGISTS’ : EXCHANGE 77 
at transversely, appears almost triangular; lip 
simple and sharp; umbilicus broad, showing 
all the volutions to the apex. Diameter, one- 
quarter of an inch. 
It is found in brooks, ditches and stagnant 
ponds, adhering to sticks and leaves. It is 
quoted from New England to Kansas, and 
southward to Washington, D.C. The only 
locality where I have found it is in a small 
pool near Hammond’s Pond, Pawtucket. Mr. 
E. H. Jenks has found several specimens in 
Valley Falls Pond. 
138. Planorbis (Gyraulus) deflec- 
tus, Say. 
Synonyms: Planorbis virens, Adams; Plan- 
orbis obliquus, DeKay ; Nautilina deflecta, 
Chenu. 
Shell dextral, depressed ; whorls five, mi- 
nutely and regularly wrinkled across; body- 
whorl somewhat carinated above; aperture 
suddenly deflected downwards; lip simple, 
commencing just below the carina and em- 
bracing but a small portion of the whorl ; 
umbilicus broad, showing one-half of each 
whorl to the apex; upper surface of the shell 
convex; lower surface concave. Diameter, 
three-tenths of an inch. 
The sub-genus, Gyraulus of Agassiz is 
represented in the United States by five species 
of which four inhabit Rhode Island. This 
section is characterized thus: ‘Shell discoidal; 
whorls few, rapidly enlarging; periphery some- 
times carinated ; last whorl sometimes de- 
flected.’ Planorbis deflectus was first col- 
lected by Dr. Bigsby in the Northwest Territory, 
and described by Say in the second volume of 
“Long’s Expedition to the source of St. Peter’s 
River,” page 261, 1824. The variety virens 
of Adams, now considered as a synonym of 
deflectus was first found by Mr. Shiverick at 
New Bedford, Mass., and described by Prof. 
C.B. Adams in Silliman’s Journal vol. XX XIX, 
No. 274, 1840, asadistinct species. It resembles 
deflectus in all respects excepting that the lip 
As not so much deflected, in fact, no more so 
than in other species of this sub-genus. 
’ 
P. deflectus is found in ponds and rivers, 
adhering to stones, Great Slave Lake to Wash- 
ington and from New England to Nebraska. 
The typical deflectus is not common in Rhode 
Island, although we find a few in Valley Falls 
Pond, The variety virens, is quite abundant 
in this locality. 
135. Planorbis (Gyraulus) dilata- 
tus, Gould. 
Shell small, of a yellowish green color; spire 
flat, composed of three whorls, separated by a 
well-defined suture; the outer whorl has a 
sharp margin ona level with the spire; below 
this margin the whorl rounds convexly so as 
to encircle a small, deep, abruptly-formed 
| umbilicus; this whorl enlarges rapidly, form- 
ing a large, not very oblique aperture; lip 
expanded, trumpet shaped. Diameter of the 
shell, three-twentieths of an inch; thickness, 
one-twentieth of an inch, 
A widely distributed shell but extremely 
local. It was first found on the Island of 
Nantucket, in damp moss by Mr. J. M. Earle 
of Worcester, Mass., afterwards in July, 1840, 
Mr. J. J. Whittemore found it in great numbers 
ina small pool in Hingham, Mass. Mr. Per- 
kins has found it at New Haven, Conn. The 
only locality in Rhode Island so far as I know, 
is a little pond on the side of the T.ouisquissett 
Pike, about half way between Providence and 
Harris Lime Rock in Smithfield. It is only 
a shallow depression, nearly dry most of the 
year, and the shells were found in summer on 
stones and at first were mistaken for some 
species of land shell, but were identified as 
Planorbis dilatatus afterwards by my friend, 
Mr. John Ford, of Philadelphia. They were 
reddish in color and not greenish as above but 
the color of all our fluviatile shells depends on 
the locality and the nature of the water in 
which they live. Another species to be de- 
scribed hereafter, whose color is given by au- 
thorities as brownish horn or light chestnut, is 
fully as often found in our State as black as: 
coal, while in some localities they are nearly 
white. 
