MUSEUM OF COMPARATIVE ZOOLOGY. BL 
Miliolina seminulum Cristellaria cultrata 
Spiroculina tmpressa C. calcar 
Vertebralina striata Sagrina columnella 
Clavulina communis Uvigerina pygmea 
C. parisiensis Truncatulina lobatula 
Textularia conica Planorbulina sp. 
T. luculenta Nonionina umbilicatula. 
T. agglutinans 
Residue, 61.91 per cent, yellowish brown, consists of Mixerals [25.00], m. di. 
0.2 to 0.3 mm. magnetite felspar, quartz, hornblende, and a few glassy fragments. 
Siliceous organisms [25.00], many Sponge spicules, a few Diatoms, one or two 
Radiolarians, and glauconitic casts of the calcareous organisms. Line washings 
[11.91], amorphous clayey matter, with fragments of casts, fine minerals, and 
siliceous particles. 
4. Specimens of deposits procured in the Gulf of Mexico and in the 
Florida Strait. 
During the years 1875, 1876, 1877, and 1878, very extensive series 
of soundings were obtained at all depths, and in all parts of the above 
areas. 
There is a very great variety in the shallow water deposits under 100 
fathoms. Near the coasts of the North American continent, where 
rivers enter, and where there are few coral reefs, the deposits are either 
sands or fine clayey muds, formed of detrital matter brought down from 
the land. Where the shores are lined by coral reefs, the deposits are 
chiefly made up of coral débris, the shells of pelagic Foraminifera and 
Mollusks and other calcareous organisms. 
The character of the deposits in depths greater than 100 fathoms is 
likewise largely determined by the greater or less proximity to the 
embouchure of rivers or to coral reefs. 
In all the deeper. deposits in the Gulf of Mexico and Strait of Florida, 
the crystalline mineral particles are very small, rarely exceeding one- 
tenth of a millimetre in diameter. They consist principally of small 
rounded grains of quartz, with fragments of felspars, mica, horn- 
blende, augite, magnetite, and rarely tourmaline. Ina few places there 
were fragments of pumice, and glauconitic particles were occasionally 
~ noticed. The mineral particles and fine clayey matter appear to be 
almost wholly derived from North American rivers. 
The carbonate of lime in the deposits of these regions is mostly made 
up of the shells of pelagic Foraminifera and Mollusks. In depths greater 
