68 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



they are as a whole of coralline or coral reef origin, as has also been 

 shown by a few hand specimens collected without reference to horizon 

 and sent to England, studied by specialists, who recognized them as 

 being of foraminiferal composition. 



Not the least important result of our researches will be a demonstra- 

 tion that the larger thicknesses of these limestones are neither of mollus- 

 can, coralline, or reef rock origin, but are foraminiferal oceanic deposits 

 and other offshore calcareous oceanic muds composed of organic detritus 

 laid down at depths below that at which reef rocks were formed and in 

 periods of geologic time prior to the appearance of the modern reef 

 building species in the sequence. 



The white limestones of Jamaica, both of the Oceanic and Coastal 

 Series, are various manifestations of the vast agency in past times of 

 animal life as extractors of carbonate of lime from sea water, similar to 

 what is now going on throughout the w^arm regions where the oceanic 

 waters are comparatively free from land sediment. That white lime- 

 stones, entirely distinct from true reef rock, are now being formed 

 throughout the tropics is a matter of common observation. Wherever 

 calcareous organisms abound around the margins of shores uncontami- 

 nated by land debris, the beach wash of calcareous material is rapidly 

 cemented by its own solutions into white limestone rock of various 

 textures ; shells into coquina ; shell debris and corals into " oolite," 

 which, when wave washed and sea sprayed, like surfaces of the ele- 

 vated reefs, indurate into hard partially crystallized surfaces. In addi- 

 tion to the near shore deposits, as shown by A. Agassiz and others, 

 calcareous muds of foraminiferal origin are being formed to depths 

 of 5,000 feet or more. When elevated into land these form white 

 limestones. 



It is also apparent that white limestones may be partially coralline, 

 as attested by well preserved coral remains, and yet not necessarily of 

 coral reef origin, or in an}^ manner connected with reef making phenom- 

 ena. All stony corals are not reef builders, and many solitary forms, 

 such as are found in some of the White limestones, inhabit oceanic 

 water to a depth of 1,000 fiithoms below the zone of 100 fathoms, 

 below which true reef building corals do not live. Yet it has been 

 customary to call any limestone with sparse traces of these solitary 

 corals *' coralline," and from this it was easily transposed into coral reef 

 rock. 



In general the tropical white limestones may originate in several 

 ways, afl shown in the following tabic. 



