280 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
the results are worked up ready for publication with the exception 
of the Carboniferous strata, which are but a small part of the whole. 
In explanation of the long time which this part has required, it 
may be stated that the area is nearly twice as great as that treated 
of in Parts 1 and 2 taken together. The geology is equally com¬ 
plex; and the topography, covering fully half the surface among the 
Blue Hills themselves, is far more difficult. It was absolutely 
necessary to walk over this part in a detailed and systematic manner, 
and to explore a large part of it repeatedly. 
Hone of the rock formations of this vicinity are of greater areal 
or structural importance than the granitic series, including the diorite 
and the various types of granite and felsite. In the study of the 
Cohasset and Hingham areas (Parts 1 and 2) Professor Crosby 
was content with general descriptions of these rocks, realizing that 
the Blue Hills complex offered a far more favorable opportunity for 
investigating their origin and genetic and structural relations; and 
it is to these problems chiefly that he has addressed himself during 
the past year. 
The amount of illustrative material in the way of specimens, 
maps, etc., collected in connection with these investigations is 
already so great as to make it desirable that a room be set apart for 
the permanent and complete exhibit of the local geology. 
Professor Crosby, and in this the Society will most heartily join, 
desires to express his gratitude to Mr. Thomas A. Watson for his 
enthusiastic assistance and encouragement in the geological inves¬ 
tigation of the Boston Basin. He has not only responded promptly 
and generously when money was needed, but has cooperated intel¬ 
lectually to the success of these investigations for a number of 
years. He has been urged to assume a share in the authorship, but 
having modestly declined, Professor Crosby wishes it to be clearly 
understood that he considers him to be justly entitled to a large 
part of the credit for whatever merit the work may possess. 
Synoptic Collection. 
This department has been making solid advances owing to the 
personal work and generosity of Mrs. J. M. Arms Sheldon. The 
worms have been worked over, fifty-three species have been care¬ 
fully studied, and fifteen figures that show the development and 
evolution of the forms selected and described. 
