456 H. 8. Williams—Life History of Spirifer levis. 
Supplementary note on the Distribution of the belts of Limestone, 
—I have given, on page 363, probable evidence that the lime- 
stone area. of northern New York Island has an eastern division 
extending down Harlem River to Kighth Avenue. I have since 
learned, from Mr. Benjamin S. Church, Resident Engineer in 
charge of the New York Croton Water Works, the confirma- 
tory fact that three of the piers of High Bridge (the Croton 
aqueduct bridge over the Harlem, crossing it near the middle 
of this part,) stand on limestone in place. I propose to pub- 
lish, in connection with the Appendix to this paper, an enlarged 
map of the north end of the Island and of the southern part of 
Westchester County, giving my observations in detail. 
(To be continued.) 
Art. L.— Abstract of some Paleontological studies of the Life History 
of SPIRIFER L&VIS H.; by Professor H. 8S. WitLiams, of 
Cornell University.* 
A CAREFUL study of the character and mode of occurrence 
of Spirifer levis H., of the Portage group of New York State, 
and comparison of it with other species of the genus, has led to 
the observation of some interesting facts bearing upon the 
probable history of the species in geological time. The orig- 
inal article embodying the results of my study was read before 
the Cornell Philosophical Society last- spring. Only a brief 
abstract of some of the important points will be attempted in 
the present article, hoping at some future time to publish the 
results in full detail. 
The important characters of the species were gathered under 
seven heads, each of which could be examined and compared 
separately with like characters in other species. 
These were: (1) Form and proportions of the shell; (2) 
the size; (8) the prominence and over-arching of the beak ; 
4) the short and high cardinal area; (5) the triangular aper- 
ture covered by an arched pseudo-deltideum ; (6) the smooth- 
ness (not plicated) of the surface; (7) the concentric series of 
minute radiating lines covering the surface. 
A careful determination of these characters as found in 
Spirijer levis was made, and the last character was specially 
noted and described. 
_ These concentric series of fine radiating lines have not been 
recorded as characteristic of the species, and so far as I know 
have not been observed by any writers on the Devonian Brachi- 
opods. Nevertheless it is an all-important character to be ob- 
* Prepared for this Journal by the author. 
