MUSEUM OF COMPARATIVE ZOOLOGY. 3 
of corals identical with those now found on the living reefs. Alacran 
Reef thus gives us an easy explanation of atols, apparently formed in 
areas of elevation, and I shall on another occasion further compare the 
structure of this interesting reef with that of the great Florida Reef, and 
of the Bahamas Bank, as I look upon it as a sort of epitome of the mode of 
formation of these extensive reefs, Taken in connection with its position 
on the Yucatan Bank, it will perhaps explain the mode of formation of the 
greater part of the Florida peninsula as connected with the bank lying to 
the westward of the mainland and to the northward of the Florida Reefs. 
Along the Cuban coast the dredge brought up a large number of si- 
licious sponges, as well as many interesting forms of Corallispongie. 
Here we found a species of Favosites, perhaps the most interesting coral 
ever dredged, and many of the corals and Gorgonis; collected by Count 
Pourtalés on the rocky plateau to the south of the Florida reefs in from 
200 to 300 fathoms, Although innumerable fragments of stems of 
Pentacrinus and portions of the arms frequently came up in the dredge, 
we were not fortunate enough to obtain a single entire specimen, but we 
obtained a young Holopus in excellent condition, While running our 
first line from Havana to Key West, we used the dredge exclusively, 
and brought up from the trough of the Gulf Stream in the deepest parts 
nothing but Globigerina ooze, apparently confirming Mr. Pourtalds’s 
results, who, in 500 fathoms' dredging over the same kind of bottom, 
had also found nothing indicating an abundant fauna. 
Subsequently, however, we used the trawl and a modification of the 
dredge over the same bottom, on the line from Cape San Antonio to 
Sand Key, and we were surprised to find an abundance of life at all 
depths, from 1,323 fathoms upwards, showing that the Globigerina ooze 
is, on the contrary, particularly rich in animal life, as Thomson and his 
associates in the * Challenger” also found it to be. Our hauls over this 
Globigerina ooze and coral ooze gave us Echinoderms, Hydroids, Polyps, 
Mollusks, Crustacea, Annelids, and Fishes; one of the most interesting 
hauls on this line was from 860 fathoms, bringing up an unusually large 
number of Lamellibranchiata and Gasteropoda of small size, but includ- 
ing many of exquisite beauty. 
The results of the hauls on the line from the Tortugas to the castern 
edge of the Yucatan Bank were perhaps the most interesting, and I had 
often occasion, while examining the contents of the trawl from our 
greatest depths to recognize old “Challenger ” friends, — forms I had be- 
come acquainted with while examining the collection of the “Challenger ” 
last winter in company with Sir Wyville Thomson. 
