BOTTOM SAMPLES, MURRAY ISLAND, THE BAHAMAS, AND FLORIDA. 285 



cent, an amount rather less than that in any of the lagoon deposits and 

 strongly contrasting with the Globigerina oozes from the Tongue of the 

 Ocean, specimens 84 and 85. The percentage of MgCOa, however, is higher, 

 being 5.03 percent. (For chemical analysis see page 270.) This is probably 

 due to the bottom-living foraminifera contributing so largely to the deposit, 

 but Messrs. Clarke and Wheeler have shown that alcyonaria and echinoids 

 are to be counted as other sources of MgCOs. Dr. Cushman furnishes the 

 following list : 



No. 100. South of Sand Key, Florida, depth 60 fathoms. Material includes gastropod 



and pelecypod shells, alcyonoid spicules, some sponge spicules, echinoid 

 plates and spines, a few pteropods, a few ostracod valves, and foraminifera 

 in quantity of Globigerina ooze types as well as bottom foraminifera. 

 Foraminifera: 



Textularia barrettii, frequent. Globigerina dubia, abundant. 



Textularia trochus, frequent. Globigerina cretacea, abundant. 



Textularia sagittula, few. Globigerina bulloides, abundant. 



Bigenerina nodosaria, few. PuUenia obliqueloculata, frequent. 



Bulimina marginata, few. Cymbalopora poeyi, few. 



Reophax scorpiurus, few. Pulvinulina menardii, few. 



Saccammina sphaerica, few. Pulvinulina elegans, few. 



Nodosaria veitebralis, few. Pulvinulina auricula, few. 



Cristellaria calcar, few. Discorbina bertheloti, few. 



Cristellaria italica, few. Nonionina umbilicatula, few. 



Marginulina costata, few. Polystomella striate punctata, few. 



Uvigerina tenuistriata, few. Amphistegina lessoni, few. 



Globigerina conglobata, frequent. Spiroloculina grata, few. 



Globigerina sacculifera, frequent. Spiroloculina arenaria, few. 



Globigerina rubra, frequent. 



This represents a type of deposit different in a number of characters from 

 the others considered. It is (a) relatively coarse grained; (b) it has a high 

 MgCOs content; (c) it is composed of both pelagic and bottom-living fora- 

 minifera, some of the latter habitat extending into shallow water. There 

 are no Orbiculina, Orbitolites, or Miliolidae. 



ELEVATED OOLITE. 



Only chemical analyses of these rocks are given (see table, page 269). One 

 of the two specimens is from Boca Grande Key, the other, from Miami, 

 Florida. If the Si02 is rejected from the analysis of the Miami oolite, the 

 Florida samples are seen to be essentially like those from the Bahamas, 

 and the remarks made on the latter, see pages 277, 278, apply to both. 



SUMMARY ON BOTTOM SAMPLES FROM FLORIDA. 



(i) Three classes of bottom deposits from Florida have been considered, 

 as follows: 



{a) Beach sand, which is mostly composed of particles of the size of 

 fine gravel (47.2 per cent) and coarse sand (46.1 per cent), and contains 

 4.3 per cent of particles of silt and clay size. Orbiculina adunca is an abun- 

 dant foraminifer. The percentage of MgCOa in the single specimen ana- 

 lyzed is 3.73. Asyet a sufficient number ofbeach sands have not been studied 



