T. S. Hunt on Laurention Rocks in Massachusetts. 75 
_Under the term cephalism we include two forms, or morphs, 
viz: (1) the cephalid, or such subdivisions of .a ae as have 
Saber pe or separating singly from the main stock (as in 
ydra and Actini), and (2) the cephaloid, or those divisions 
of a fissigemmating body which do not contain a complete 
ArT. X.—On Laurentian Rocks in Eastern Massachusetts; by 
Dr. T. Srerry Hunt, F.R.S. 
IN a paper read before the American Association for the 
Advancement of Science at Washington in April, 1854, and 
published in this Journal for September in the same year, (vol. 
Xvi, page 193,) I noticed the crystalline limestones of north- 
eastern Massachusetts, which weré described by the late Dr. 
tchcock as enclosed in the great gneissic and hornblendie forn 
