191Ji\ Proceedings IST. C. Academy of Science 63 



ECONOMIC GEOLOGY OF CHAPEL HILL, N. C. AND VICINITY. 



John E. Smith 

 Generalized Section of Mantle Rock. 



1. Soil, "Top Soil," red to gray or black i to 3 feet 



2. Subsoil, fine, somewhat compact, red to yellow clay 3 to 10 feet 



3. Clay, coarse and lumpy, with some sand 5 to 20 feet 



4. "Natural Sand-Clay," feldspar, quartz, sand and clay.... 10 to 20 feet 



5. Fragmental Rock, angular, decayed, size 2 to 4 inches.... 10 to 20 feet 



6. Fragmental Rock, coarser and fresher than that in 5.... 5 to 15 feet 



7. Granite, "Bed Rock," "Country Rock." 



This region serves as a type for Piedmont areas in which granite is 

 the underlying rock — about one-third of the Piedmont Belt. 



Zone No. i is the surface soil of the upland and is used in agriculture 

 and in road building. No. 2 provides clay suitable for brick and tile. 

 As the topography is mature and these zones have been removed by ero- 

 sion from much of the area, the value of the land is low. The material 

 of zone 4 makes good sand-clay roads. This is approximately horizontal 

 and outcrops on the slopes where valleys have been cut below its depth. 

 Stream sand is used in making mortar and in road construction. 



This mantle rock forms an excellent filter and most wells in it are 

 free from contamination. Excepting the mountain region, these are the 

 most healthful areas in the South. 



AN ACHLYA OF HYBRID ( ?) ORIGIN 



W. C. COKER. 



An Achlya was described from Chapel Hill, N. C. with pecularities 

 that suggest a hybrid origin. The tips of the hyphae often die and the 

 growth is then extended as a side branch below the dead tip. The 

 spores show a strong tendency to poor organization, the protoplasm often 

 segregating only imperfectly, and producing irregular masses of various 

 sizes. The same is true of the eggs, which are of any size and almost 

 never become perfectly organized, and die quickly. The plant seems most 

 like Achlya polyandra Hildeband, but differs from it in the walls of the 

 oogonia being pitted and in the abnormal behavior of the eggs. 



It is suggested that the plant may be a hybrid between A. DeBaryana 

 Humphrey and A. apiculata DeBary. 



THE NURSE SHARKS OF BOCA GRANDE CAY, FLORIDA. 



E. W. GUDGER. 



Boca Grande Cay is an island of coral sand and mangroves lying about 

 20 miles west of Key West. Situated on a shallow submarine platform, 

 about 120° of its circumference is surrounded by sand flats inhabited 



