PREFATORY NOTE. 
During the progress of Vol. V, part ii, some new material came into the hands 
of the author, as well as better specimens of some forms already described and 
illustrated. In order to render available the knowledge thus acquired, a few 
supplementary plates were lithographed, with the expectation of being permitted 
to publish them, with the necessary text, within a short time after the appear¬ 
ance of the volume at the end of 1879. Unforeseen obstacles in the way of 
any publication prevented these being made available, and this interruption 
finally prevented the completion of the Supplement upon the plan originally 
intended. The material thus prepared was laid aside, and the manuscript notes 
and observations, made at that time, preparatory for the printing, were mislaid 
or lost. 
In 1883, after the passage of the law to limit and complete the Palaeontology 
OF New York, provision was made for incorporating these plates, with the 
necessary descriptive matter, into the work, as a supplernentary part of Volume 
YII, where they now appear. The plates are numbered in consecutive order 
from cxiv to cxxix inclusive, the last plate of Vol. V, part ii, being cxiii. A 
single plate is devoted to the more complete representation of the Pteropoda, 
embracing figures in farther illustration of some species already described, 
together with others of new forms. 
During the progress of Vol. V, part ii, the study of the Pteropoda, especially 
of the genera Tentaculites and Styliola, had suggested the importance of a 
review of these genera and an inquiry into their relations with Cornulites. 
It was not until the discussion of the genus Tentaculites had been nearly 
completed, and the tabular arrangement of species in type, that the author 
became fully aware of the necessity of this revision and of a farther inquiry 
