THE - CONCHOLOGISTS’ - EXCHANGE. 
79 
valve, is a strong lateral tooth, fitting into a 
deep pit in the right valve; surface covered 
with faint lines of growth; color white under a 
thin dirty brown epidermis; interior clear white, 
glossy. Length ¥% inch, height 54, breadth ,. 
Described by Say in the Journ, Acad. Nat. 
Sci., Phila, ii. 309,1822. Inhabits from Maine 
to Florida, and along the northern shores of 
the Gulf of Mexico to Texas. This is an ex- 
traordinary range for any species of mollusca, 
not more so in point of miles, perhaps, than 
others which inhabit both sides of the Atlantic 
Ocean through the Polar regions, but in the 
extremes of climate, from our colder shores to 
the almost tropical waters of the Gulf. It is 
quite abundant in R. I., found on our sandy 
beaches, and also dredged in a few fathoms of 
water, 
To be Continued. 
DESCRIPTION OF NORTH AMERICAN 
SHELLS. 
BY iC) be “ANCE. 
6.—Helix commutanda, Anc. 
This name I propose for Triodopsis Harford- 
iana, W. G. Binney (not Helix (Doedalochila) 
Harfordiana, Cooper). The names of Polygyra, 
Deedalochila, Triodopsis, ete., as shown by W. 
H. Dall, are merely sectional and zo0¢ generic, 
hence it becomes necessary to change Binney’s 
name, as Iam confident the two Harfordiana be- 
long to the same group. 
7 —Helix (Polygyra) unguifera, Mouss. 
H. unguifera, Mouss. in Journ. de Conch., 
1883, p. 216, fig. 
This shell, found in the vicinity of Mazatlan 
(Cinaloa), Mexico, by Mr. Forrer, appears to 
be the same as 4, acutedentata, \V. G. Bin- 
ney (Proc, Ac. Nat. Sc., Phil., 1857, p. 83) 
said to have been found at Mazatlan and Guay- 
mas; at least it may only be a smaller variety 
distinguished from the type by its smaller size, 
= = 
5% instead of 6 whorls and in having the hook 
on the superior tooth and not on the inferior 
(as stated, perhaps erroneously, by Binney). 
$.—Helicina Durangoana, Mouss. 
Anc. p. 218, 1883. 
This is perhaps the same shell as the one 
found by Mr. Xantus in the Sierra Madre (fig. 
in Binney’s Land and Freshwater Shells of 
North America). As Mr. Mousson’s diagno- 
sis is incomplete in regard to the peculiar sculp- 
ture and operculum of this species, I give the 
following description from authentic specimens 
in my collection: 
Testa imperforata, depresso-conica, subnitida, 
glabrata, solidula, luteo-albida aut candida, 
scepe ad summum luteo tincta; Apertura intus 
pallida, pariter luteola. Spira late conoidalis, 
apice subobtusa; anfractus, 6; lineis exilibus 
subverticalibus undulatisque, confertim vixque 
perspicue (ad apicem evanescentibus) sub lente 
sculpti; proeterea obsoletis nonnullis remotisque 
spiralibus lineolis exorati; subconvexi, regulari- 
ter et sat rapide crescentes, ultimus in medio 
obscure rotundeque angulosus, infra convexus. 
Apertura semirotunda, externe obtuse angulata, 
basi ad columellam angulatim  unituber- 
culata. Peristoma incranatulum,  tenuiter 
expanso-reflexum. Callum columellare de- 
pressum, nitidum. Operculum — rubellum 
semitestaceum. 
Diam.: 9% mill. 
9.—Liogyrus Lehnerti, Anc. 
Testa subconoidea rimata, solidiuscula, sub- 
virenti-hyalina, vel cornea, sinistrorsa, nitida, 
sub lente striatula, glabra spira apice valde ob- 
tusa ; anfractus 4, rapide, sat regulariter tamen 
crescentes, tumidi, rotundati, sutura profunda ; 
primo depresso, penultimo turgidulo; ultimo 
ad peripheriam inflato, dimidium testoe fere 
adcequante, subtus convexo, ad aperturam 
haud solutam regulariter descendente. Aper- 
tura fere recta, subcircularis-oblonga, superne 
et inferne obscure angulata, marginibus contin- 
Wis." 
Long.: 3%4, lat.: 3% mill, 
