182 SUBTERRANEAN WATER WAYS IN THE BAHAMA ISLANDS. 
the shell named Pupa martensi Weind, inasmuch as this name and 
that of P. martensiana are often confused, and I have even seen speci- 
mens of Strophia agrestina labelled as S. martensi. 
S. martensi is a very peculiar shell, differing from most species of 
the striated Strophias in having a regular constriction to the 
striations, near the sutures, thus somewhat isolating a series of 
rounded knobs above each suture (there may, however, be more than 
one species so characterized), resembling, somewhat, a form of the little 
S. nana, figured on Plate II, fig. 11, B r Yol. 1, of these Contributions 
(See also description, page 28). 
HABITS AND DISTRIBUTION. 
The Grass Strophia occurs on the south side of New Providence, 
about opposite of the city of Nassau but distant from it some six 
miles. They live in pine woods, among which grow scattering palms, 
about a half mile from the shore, and occur under stones, fallen palm 
leaves, shrubs, etc., or are found clinging in clusters among the tufts of 
grass of which there is a scanty growth in this locality. I cannot give 
the exact range of this species, but I have traced it for several hundred 
yards along the two roads which go to the south side beach. 1 have 
found them on two occasions, one in February, 1884, and then in 
March, 18-43. On both occasions they were quite abundant. 
SUBTERRANEAN WATER WAYS IN THE BAHAMA 
ISLANDS. 
That the Bahama Islands are of comparatively recent origin, 
geologically considered, will be doubted by no one who has given the 
matter any attention. That their existence is also due largely to the 
coral polyp is quite obvious, for when we come to examine the keys 
which make up this group of islands we find that all of them not only 
show marks of having once been sunken reefs of coral, but many of 
them are nnmistakeably elevated atolls. I say elevated, for on many 
of the beaches, or sea borders, we find every evidence of two up- 
heavals, possibly at not very wide intervals apart. That is, we have 
the present level of the higher hills and land, and on many of the 
keys, an old beach, or high water mark, exhibited by blocks of coral 
