6 BULLETIN OF THE 
Yulf of Mexico at similar depths. This is the more important because 
the hydrography of the gulf is now, as you well know, so far advanced 
that when the present season is finished, and the results are plotted, 
we shall have a hydrographic chart with accompanying temperature 
profiles in sufficient number to give an admirable account of the Physi- 
cal Geography of the Gulf of Mexico. 
I was very much struck, on first seeing the ooze of the deep water of 
the Straits of Florida between Havana and Florida Keys, with the im- 
mense number of dead Pteropod shells which it contained, in addition to 
the countless tests of Globigerins and Orbiculine. These shells belonged 
mainly to the genera Clio, Hyaleca, Triptera, Atlanta, Styliola, etc., all of 
which swarm on the surface, or a little below it, in all the parts of the 
Gulf of Mexico which we have thus far passed over. I could at once see 
how important a part these dead shells of Pteropods would play in the 
formation of the sedimentary matter accumulating at the bottom, Globi- 
gerine and Orbiculine form, as we know, the bulk of the ooze, but the 
remaining part of the mud is made up mainly of the dead shells of 
Pteropods in all stages of disintegration, from perfect shells, still filled 
with the decaying animals, to the most minute grains, in which we can 
just detect the presence of the Pteropod test. This composition of the 
ooze was the universal rule in all specimens of the bottom which I have 
had thus far time to examine. This plainly shows that Pteropods as well 
as Globigerinso and Orbiculine, with other pelasgic animals swarming at 
the surface of the sea at great distances from the land, are an important 
factor in the composition of all the deep-sea deposits going on at the pres- 
ent day. Of course they must have played a similar part in the deposition 
of amorphous limestone formations in former geological periods. Whether 
this decomposition of the test becomes more rapid with increasing depth, 
as is the case in the deep-sea red clay of the “Challenger,” I have not yet 
been able to ascertain, from the rapid examination of the samples of 
bottom thus far obtained. To show how far the dead Pteropod shells 
make up the Globigerina ooze, I took, from the contents of the trawl 
from 860 fathoms, equal portions of mud as it came up; one part was 
left and roughly measured, the other was first carefully sifted, the Ptero- 
pod shells and their fragments were then collected, and likewise meas- 
ured, when their bulk was found to be somewhat more than half the 
bulk of the sifted mud from which they came. This mud was intensely 
cold, and it was a strange sensation to have your back and head burn- 
ing under the scorching rays of the sun, while handling, with benumbed 
fingers, the ice-cold masses of mud of 393° Fahrenheit, brought up by 
the dredge. 
