THE AMERICAN 



MONTHLY 



* 



MICROSCOPICAL JOURNAL 



Vol. IV. 



Boston, January, 1883. 



No. I. 



The Nummulites of North 

 America. 



In the last number of the Proceed- 

 ings of the Academy of Natural Sci- 

 ences of Philadelphia, is an article by 

 Mr. Angelo Heilprin, on the Nummu- 

 lites of Florida, upon which this article 

 is based. The nummulites, as the 

 reader will doubtless know, are a genus 

 of the Foraminifera which grow in a 

 spiral, the outer whorls more or less 

 completely enveloping the inner ones. 

 The interior of the shell is divided up 

 into successive chambers by septa. 

 Although the fossil nummulites are 

 very abundant and very large in some 

 parts of the world, none have been 

 positively identified in North Ameri- 

 can strata. A species has been de- 

 scribed as occurring in Florida under 

 the name N. floridanus, but, from 

 the imperfect accounts published, it 

 seems probable that this form should 

 be placed among the Orbiculina. In 

 examining the rock in which the so- 

 called nummulite was said to be found, 

 no trace of its existence was discover- 

 ed, but another ioxYc\,ApercuUna rotella, 

 was quite abundant. There were, in- 

 deed, disciform bodies found, measur- 

 ing about a quarter of an inch in 

 diameter, which might be taken as a 

 form of foraminiferal test, but they 

 were in such an imperfect state of 

 preservat'on that nothing definite 

 could be made out of them. 



The late researches of the author of 

 the paper referred to, have conclusively 

 proved the existence of nummulites in 

 Florida. The rock in which they were 

 found was obtained from the western 

 shore of the peninsula of Florida, a 

 yellowish-white, friable limestone, in 



the vicinity of Cheesowiska River, 

 Hernando County, about four miles 

 from the coast line. In some places 

 they are so abundant as to constitute 

 masses of a true nummulitic rock. 



All the specimens appear to belong 

 to the same species, Numj7iulma Wil- 

 coxi, n. sp. It is described as follows : 

 Test regularly rounded, tumid, meas- 

 uring in the largest specimens ^ of 

 an inch in diameter ; external surface 

 distinctly marked by the arcuate and 

 wavy outlines of the septal prolonga- 

 tions, volutions about 5, completely 

 enveloping, septa close set, about 35- 

 45 in the last whorl, and well flexed ; 

 initial chamber distinct. In the illus- 

 tration, the first figure shows the form 

 of natural size, the second is an en- 

 larged view. 



NumuUina Wilcoxi. 



There is still an interesting geolog- 

 ical question to be decided concerning 

 the age of the deposit in which the 

 nummulites are found. That they 

 are not in their original position is 

 proved by their association with land 

 and fresh water shells of a much later 

 period than the age of nummulites, 

 which are seldom, if ever, found later 

 than the eocene or oligocene deposits. 

 It is probable that the rock from which 

 they were originally derived, will be 

 found along the border of the gulf, 

 possibly submerged. 



