‘ 
1386 A. EF. Verrill—Results of recent Dredging Expeditions 
Hydroids. 
Sertularia pumila. |Obelia geniculata. | Clava leptostyla. 
OUP 
Metridium marginatum. 
St. Lawrence, and many of them to the Arctic Ocean, North 
Pacific, and northern Europe, they all extend as far south as 
Long Island Sound, and several of them even to North Carolina. 
Most of them are, therefore, northern species having a wide dis- 
tribution, and their presence in this particular locality has no 
special significan 
Is). 
at at a more remote period, the marine climate of this 
region was still warmer,* and the southern species were more 
abundant than during the period when the Indian shell-heaps 
were formed, is shown by the occurrence of great beds 0 
oyster shells a few feet beneath the mud in Portland Harbor, 
where they are associated with quahogs and several other south- 
ern species, among which are Callista convexa, Turbonilla wnter- 
rupta, and Pecten irradians. The latter is not known to live, 
at present, north of Cape Ann, on the New England coast. It 
is absent, apparently, from the colony in the Gulf of St. Law- 
rence, as well as from that of Quahog Bay. It is very rare 
north of Cape Cod.+ 
* The evidence here given is probably applicable chiefly to the temperature of 
the warmer months, or more properly to the reproductive season of the mollusks 
to, for the climatic distribution of most marine animals seems to depen’ 
mainly on the temperature of the at which reproduction tak . 
in nom 
without mentioning the special locality. It may, perhaps, occur in some of 
sheltered localities near Halifax, where another southern colony exists. 
