24 SHELLS OF NEW ENGLAND. 
CORBULIDA. 
CorsuLa contRacTa, Say. Gould, 43, f. 37. — Lamin. 
From Cape Cod southward. 
MYADZE. 
GiycyMeEris stniqua, Lam. Gould, 39. Mya siliqua, 
Chemn.— Corall. From Cape Cod northward. Na- 
hant Beach, alive, after a storm, (W. 8.) Province- 
town Harb. (‘Tott.) 
Panopxa Norveetca, Lovin. Mya Norvegica, Spengl. 
Panopea arctica, Desh. Gould, 37, f. 27.— From 
the Banks. 
Mya truncata, Lin. Gould, 42. — Litt. to Corall. 
Eastport at low water, among pebbles, (W. 8.) and 
southward to Cape Cod. 
M. arenaria, Lin. Gould. — Litt. Whole Coast. 
GASTROCHAENID. 
PetTrRicoLaA PHOLADIFORMIS, Lam. 1818. Gould. P. 
fornicata, Say, 1821.— Litt. Whole Coast. 
P. pactyLus, Say. Gould, 65.— Litt. Cape Cod to 
N. Y. I have found the differences between this and 
the preceding species, mentioned by Dr. Gould, to be 
inconstant, but I defer to his authority in regarding 
it distinct. 
The propriety of placing this genus among the 
Gastrochenide may be questioned. Our species 
have very robust siphons which are sometimes ex- 
