TITLES AND ABSTRACTS OF PAPERS 215 



limb is not primitive, and that the modern Branehiopoda are not so nearly 

 allied to the trilobites as the Copepoda are. Relationships to the Arachnida, 

 Diplopoda, Chilopoda, and Insecta are pointed out. A renewed study of the 

 bodily form of the trilobite shows that it is not so specialized as has been 

 supposed, and that it is capable of modifications which allow a consideration 

 of these animals as the possible ancestors of the other Arthropoda. 



The results of studies on the formatiou of coquina followed, with the 

 authors remarks illustrated by lantern slides. Discussed by Dr. T. 

 AVayland Vaiighan, with replies by the author. 



ORIGIX OF THE "BEACH ROCK" (COQUIXAJ AT LOGGERHEAD KEY, TORTUGAS 



BY RICHARD M. FIELD 



(Abstract) 



Through the kindness of Dr. Alfred G. Mayer, the writer was enabled to 

 visit the Tortugas group for the purpose of studying the conditions of sedi- 

 mentation on and near the "coral" reefs. Among other studies, an attempt 

 was made to discover the origin of the "beach-rock" or cemented shell-sands 

 which occur between high and low tides. By means of a stand-pipe and pump, 

 it was found that during heavy rains a shell key acts like a reservoir, and 

 that the meteoric water (to which an appreciable amount of humus acid is 

 added as it passes through the surface layers) dissolves CaCOs on its way 

 down through the loose shell sands. The ground water, which lies just above 

 the salt or brackish water zone, was found to contain 40 per cent more CaCOg 

 in. solution, or colloidal suspension, than the normal sea water. This concen- 

 trated solution of CaCOa has a strong cementing value, and is probably an 

 important factor in the formation of the "beach-rock" where the ground water 

 flows out through the beach sands, between tides. 



A curious similarity of foraminifera in the Upper Vicksburgian of 

 Afississippi and the recent waters of the Indo-Pacific region formed the 

 subject of the next paper. 



lOR.AMIXIFERAL FAUX A OF THE BYRAM MARL 

 BY .JOSEPH A. CUSHMAN 



(Ahstract) 



A study of the foraminifera of the marl at tne type station Byram, Missis- 

 sippi, has shown a fauna consisting of nearly seventy (70) species. Nearly 

 half of these are undescribed ; of the others most of them are either now living 

 or represented by a closely allied species in the shallower waters of the Indo- 

 I'acific region. Some of the species are also found in the Mint Spring marl 

 and in the Red Bluff clay, the lower members of the Lower Oligocene. 



Dr. Vauglian next presented a digest of his stratigraphic studies on 

 certain parts of the West Indies and Central America, illustrating his 

 remarks bv lantern slides. 



