iS 9 x.] 
309 
[Upham 
northward limits at Cape Cod or in Massachusetts Bay, and in 
one instance near Portland, Maine ; excepting that several of 
them occur in isolated colonies far north of their general and 
continuous range, as in Casco and Quahog bays, Maine, and es- 
pecially in the shallow southern part or Acadian Bay of the Gulf 
of St. Lawrence, from Cape Breton Island to the Bay of 
Chaleurs . 1 The occurrence of these southern mollusks, which 
are mostly now absent or local and rare north of Cape Cod, shows 
that the sea here during some part of the Recent epoch has been 
warmer than at the present time. Six of the fourteen, namely, 
Ilyanassa obsoleta, Urosalpinx cinerea , Mulinia lateralis , Venus 
mercenaria , Modiola plicatula, and Ostrea virginiana, are found in 
each of the three localities noted and indicate the contempo- 
raneousness of these deposits. All of the eleven northern species, 
some of which extend to the Arctic Ocean, but including one 
found only on the coast of New England, range to south- 
ward limits beyond Cape Cod. In short, the temperature of the 
sea in Massachusetts Bay and in the estuaries of its rivers, at 
the time represented by these deposits, was evidently like that of 
the sea now on the southern coast of New England, which, be- 
sides the increase of the sun’s heat due to the lower latitude, 
receives some contribution from the warmth of the Gulf Stream, 
whereas the waters of the Gulf of Maine and Massachusetts Bay 
are chilled by a coastal current from the north. 
The relative heights of land and sea were apparently almostJ.the 
same as now. Every one of the twenty-five recorded species 
flourishes on the shore between the levels of high and low tide, 
or at the plane of extreme low tide, or in shallow water of a few 
fathoms. In the list of each locality are species that prefer a 
1 After the presentation of this paper before the Society, the author learnediof Mr. 
W. F. Ganong’s admirable memoir, “Southern Invertebrates on the Shores of Acadia,” 
published a few months ago in the Transactions of the Royal Society of Canada, vol. 
viii, sec. iv, for 1890, pp. 167-185. Mr. Ganong gives a history of the discovery of the 
character of the colonies ; a list of the marine invertebrates belonging to the Virginian 
fauna, which occur upon the coasts of Acadia and Maine, with tabular reference to 
their known localities ; and a discussion of their recent extinction on intervening por- 
tions of the coast thence south to Massachusetts Bay and Cape Cod. He accepts the 
explanation of Verrill and Dawson, noticed on a following page, for the present re- 
frigeration of the sea here ; but also points to the recent increasing severity of cold in 
Greenland and Iceland, and suggests that the marine currents there likewise have 
been lately warmer than now. 
