BOTTOM SAMPLES, MURRAY ISLAND, THE BAHAMAS, AND FLORIDA. 28l 



BEACH SAND FROM SANDS KEY. 



The mechanical analysis (sample No. 68) shows that 93.3 per cent of 

 the material is between 2 and 0.5 mm. in diameter, while there is 4.3 per 

 cent of silt and clay size. According to the partial chemical analyses, page 

 270, there are 3.73 per cent of MgC0 3 and 95.08 per cent of CaC0 3 . There 

 is less MgC0 3 than in the material behind Cocoanut Point Reef, but more 

 than in the finely divided muds in South Bight and off the west side of Andros 

 Island. 



The following is a list (by Joseph A. Cushman) of the foraminifera from 

 beach sand from east side of Sands Key, Florida, No. 68 : 



No. 68. Beach sand from east side of Sands Key, Florida. 



Orbiculina adunca, abundant. Clavulina angularis, few. 



Orbitolites marginalis, few. Trochammina inflata, one. 



Peneroplis pertusus, few. Verneuilina affixa, one. 



Quinqueloculina agglutinans, few. Discorbina vilardeboana, one. 



Triloculina linneiana, few. Planorbulina mediterranensis, few. 



Biloculina carinata, few. Quinqueloculina, etc. 



The foraminifera in the beach sands on the sea face of keys seem 



rather consistently to be nearly the same species. Those found on Lisbon 



Beach, Mangrove Cay, South Bight, Andros Island, Bahamas (identifications 



by Dr. Cushman), are as follows: 



No. 90. Beach sand from Lisbon Beach (east of mouth of Lisbon Creek), South Bight, 

 Mangrove Key, Andros Island, Bahamas. Material fragmentary and water- 

 worn. 



Foraminifera: 



Orbiculina adunca, frequent. Triloculina linneiana, one. 



Quinqueloculina agglutinans, few. Quinqueloculina sp. 



Verneuilina affixa, few. 



The beach sands, naturally, are the coarsest material in the areas 

 here considered. The sizing varies according to local conditions of winds, 

 currents, etc., and as yet has not been adequately studied. The composition 

 also varies from place to place, according to differences in the organisms 

 from which the sands are derived. Efforts are under way to ascertain the 

 sources of the components of a number of beach sands taken from selected 

 localities. 



LAGOON SAMPLES. 



Sample from between Loggerhead and Cudjoe Keys. 

 According to the mechanical analysis, 64.5 per cent of specimen No. 

 91, from between Loggerhead and Cudjoe Keys, is of silt and clay size, nearly 

 the same percentage as in the fine muds in South Bight and west of Andros 

 Island (see plate 94); the percentage of MgC0 3 is 2.87, also nearly the same 

 as in the Andros Island specimens. The following is a list of the foraminifera 

 (identification by Dr. Cushman): 



No. 91. Mud flat, dredged material, north side of Loggerhead Key, east of Sugar Loaf Key. 

 Foraminifera: 



Polystomella striatopunctata, most Orbiculina adunca, few. 



frequent species. Triloculina linneiana, few. 



Quinqueloculina agglutinans, frequent. Quinqueloculina and Triloculina sp. 



This obviously groups with the Bahaman specimens mentioned, Nos. 

 79, 87, 88, and 177. 



