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288 American Seashells
Superjamily PYRAMIDELLACEA
Family PYRAMIDELLIDAE
This is a well-known family of very small gastropods which are ex-
tremely baffling to novices attempting to identify any one of the several hun-
dred so-called species. Even among the experts there is not always agreement
on what constitutes a species, subgenus or genus in this group. It would be
impossible to present in a book this siz^e even an account of only the most
common species. Those interested in delving into this interesting maze of
species are referred to the works of Bartsch, W. H. Dall and K. Bush.
The recent work of Fretter and Graham has shown that the Pyrams are
ectoparasites, with each species feeding on a particular host, usually a tubico-
lous polychaete worm or a bivalve mollusk. The Pyrams attach themselves
ATLANTIC COAST PYRA.MIDELLIDAE
(Figure 62)
(The names in parentheses are subgenera. Illustrations are from P. Bartsch,
1909, Proc. Boston Soc. Nat. Hist., vol. 34, no. 4. The measurements refer to the
length of an average specimen).
a, Odostojjiia (Chrysallida) ivillisi Bartsch. Willis' Odostome. 3 mm.; milky
white. Prince Edward Island, Canada. Uncommon.
b, Turbonilla (Pyrgisais) internipta Totten. Interrupted Turbonille. 6 mm.;
pale waxy yellow. Casco Bay, Maine, to the West Indies. 2 to 107 fathoms.
Common.
c, Turbonilla (Tiirbo?iilla) stricta Verrill. Varied Turbonille. 5 mm.; milky
white. Massachusetts to North Carolina. 3 to 8 fathoms. Moderately common.
d, Turbojiilla (Tiirbo?iilla) iiivea Stimpson. Snowy Turbonille. 5 mm.; milky
white. Maine to Connecticut. 40 to 400 fathoms. Uncommon.
e, Pyra7indella (Syrnola) fiisca C. B. Adams. Brown Pyram. 6 mm.; light brown.
Gulf of St. Lawrence to Florida. Common.
f, Odostomia (Menestho) trifida Totten. Three-lined Odostome. 4 mm.; shiny
white. Maine to New Jersey. Shore. Common.
g, Odostojjiia (lolaea) heiidersojii Bartsch. Henderson's Odostome. 3 mm.; glossy
white. Woods Hole, Massachusetts. Uncommon.
h, Odostomia (Menestho) bisutiiralis Say. Double-sutured Odostome. 5 mm.;
milky white. Nova Scotia to Delaware Bay. Shore to 2 fathoms. Common.
i, Odostomia (Menestho) impressa Say. Impressed Odostome. 5 mm.; milky
white. Massachusetts Bay to Gulf of Mexico. Common in shallow water.
j, Odostomia (Chrysallida) sejniniida C. B. Adams. Half-smooth Odostome.
4 mm.; whitish. Nova Scotia to Gulf of Mexico. Shore to 12 fathoms.
Common.
k, Odostomia (Odostomia) gibbosa Bush. Fat Odostome. 3 mm.; shiny, yellowish
white. Maine to southern Massachusetts. Uncommon. (= modesta'^2iXX.sc\\y
not Stimpson)