ie - CONCHOLOGISIS! EXCHANGE: 63 
This species was described by Couthouy in 
the Jour, Bost. Soc. Nat. Hist. 11: 183, 1839. 
It is said to inhabit the whole New England 
coast. It is thrown up in storms on Chelsea 
Beach, containing the living animal. Gould says: 
« Single valves are found on R. I.” I have 
never seen one in our bay. A shell of this 
size, growing sometimes” to four inches in 
length, would not be easily overlooked; it is 
shaped much like a quahog, but its narrowed 
and truncated posterior would at once distin- 
guish it, without looking for the minor differ- 
ences, such as the convexity of one valve, the’ 
toothless hinge, etc. Verrill says: “ This 
species burrows so deeply in the mud or sand 
that it is seldom taken alive with the dredge.” 
154.— Thracita truncata, Mighels and Adams. 
Shell small, ovate-triangular, compressed’ 
white, solid, beaks at the posterior fourth’ 
small, the right one excavated to receive the left ; 
surface covered with lines of growth; epider- 
mis pale yellowish; interior white; ligament 
large. Length, three-quarters; height, one- 
half ; breadth, three-tenths of aninch. Described 
by Mighels and Adams in the Journ. Bost. Soc. 
Nat. Hist. 1v: 38, 1842. A deep waterspecies 
Rhode Island. 
not *yet found in Agassiz 
dredged it off Martha’s Vineyard. Inhabits 
from Long Island to Greenland. 
To be Continued. 
DESCRIPTION OF NORTH AMERICAN 
SHELLS. 
BY C. F. ANCEY. 
1.—Helix Verrilli, Anc. 
Testa utrinque convexa, depressiuscula, niti- 
dula, sat minute umbilicata, subopalino-albida, 
subhyalina, in medio ultimi zona angusta fusca 
cincta. Spira depresso-conyexa, summo obtuso, 
nitido, leevigato , Anfractus fere 4%, modice 
et regulariter accrescentes, convexi, sutura 1m- 
pressa linearique divisi, supra (apice excepto) 
granis breviter piligeris regulariter in quincun- 
ciis dispositis infra evanidis prcediti? embryo- 
nali magno, haud papillatim producto, subtus 
regulariter convexo, nitido (striis incrementi 
vix perspicuis sculpto), ad aperturam leviter 
paulatimque antice descendente. Apertura 
sub-obliqua, emarginato-circularis, ad Casin 
prope columellam obscure subangulata. Peris- 
toma tenuiter expansum, ad columellam latius 
reflexum, album, umbilicum ptofundum ex 
parte subobtectans. 
Diam. maj., :17% 5 min., :15)4 ; alt., 1174 
mill, 
Locality: Ventanas, Durango, N. W. Mex- 
ico. 
This beautiful shell, named after Prof. Ver- 
rill, belongs to subg, Leptarionta, Crosse.” It 
was collected by M. Forier and identified by 
Prof. Mousson as 4. Remondi, Tryon, from 
which it widely differs. Indeed, they do not 
seem to belong to the same group, as Verrilli is 
quite distinct in shape, color, texture, number 
of whorls, etc. It also differs much from 
another species, which has been erroneously re- 
ported ‘from Arizona, and subsequently found 
in Lower California by M. W. H. Gabb, and 
also more recently in the same peninsula by a 
French engineer, Mr. Cumenge, associated 
there with Leptobyrsus spirifer, Gabb, a much 
more common shell, at El Boleo on the coast 
opposite to Guaymas, in Sonora, viz: Helix 
Rowelli, Newcomb, in having a much smaller 
umbilicus, less depressed shell, higher body 
whorl, and the upper whorl not abruptly ele- 
vated above the level of the spire. 
2.—Helix Levettet, Bland. 
Triodopsis Levettei, Blandin Ann. Sc.Ac.N, 
Y.ii, p. 115 (1880). 
The type was found in Santa Fe Canyon, 
New Mexico; thespecies has been subsequent- 
ly reported by Mr. W. G, Binney as found in 
the Huachuca Mountains, near Tucson, Arizo- 
na, (vide : Bulletin of the Museum of Comp. 
Zool., Cambridge, Dec., 1886, p. 36, pl. 1, fig. 
15). The specimen figuredin the last said 
publication differs from the type as represented 
in the “ Manual of American Land Shells,” 
1885 (p. 385, fig. 418), in having a slightly 
