132 
MONOGRAPH OF THE GENES STROPHIA. 
form No. 1 of S. coryi, there is a decided tendency to a reversion 
towards S. cinerea, in fact, I have two specimens which are nearly or 
quite typical S cinerea. I do not hesitate to affirm with these facts in 
view, showing so clearly the relationship of the two species, that S, 
coryi, as found on the west end of New Providence, is derived from S. 
cinerea. Now comes the question as to where the specimens of 
S. coryi which I found on Spruce Key came from. Has S. cinerea 
evolved two colonies of S. coryi, one for Spruce Key and one for the 
west end of New Providence? 
The presence of a species of Strophia evolved from S. cinerea on 
the west end of New Providence is accounted for by supposing, quite 
reasonably, that the parent stock was transported there by the 
persons who settled on the plantation which is now there, the house of 
which I have'spoken as being near the colony of Strophia coryi. 
Now in regard to the specimens of S. coryi, found on Spruce Key, 
it seems more reasonable to suppose, that they also were evolved 
directly from the parent stock of S. cinerea, possibly through form No. 
3, than to suppose that they were transported from the west end of 
New Providence, some twenty miles away. The shells from Hog 
Island could have reached Spruce Key through the agency of ocean 
currents, as will be seen by consulting the diagrammatic chart given 
in fig. 40. 
The scale of this chart is, roughly estimated, about two inches to 
the mile. A, is Hog Island, e, Middle Bay, the home of typical S. 
cinerea, C, is Spruce Key, but as the tide sets east an I west through 
Nassau Harbor, in the ebb and flood, and north and south through the 
Narrows, N, between Hog Island and Long Island, B, a shell falling 
into the water at c, would quite possibly reach Spruce Key on the 
ebb tide. 
In order that the reader may more fully comprehend the 
localities inhabited by the interesting species, sub-species and forms 
of Strophia, in the immediate neighborhood of Hog Island, 1 give the 
accompanying diagrammatic chart. 
E, is a portion of New Providence, east of Spotter’s Key. A, is 
the cemetery, and the locality bordered by the dotted lines, shows the 
range of S. curtissii, extending as far east as Waterloo, b. In the 
midst of these bounds, and in the cemetery, is the limited range of S. 
ihorndikei, t. 
Leaving the main island of New Providence, we cross to Spotter’s 
Key, the eastern end of which is shown at D. This is the home of the 
