tHE 
AMERICAN NATURA ISS 
VoL. XXXII. January, 1898. NO. 373- 
II NOPSIS OF RECENT PROGRESS IN. THE 
SIUDY OF GRAPTOLITES. 
Dr. R. RUEDEMANN. 
THE graptolites have been a puzzling group of fossils to 
palzontologists ever since they were discovered. Though on 
account of their excessive abundance in certain strata, the 
beauty and variety of their delicate forms, and the strange mode 
of their vertical and horizontal distribution they have always 
received a full share of attention, the knowledge of their mor- 
phology has made only little progress, owing to their preserva- 
tion as completely flattened carbonaceous films. As a result 
of this incomplete knowledge of their structure, the systematic 
conscience of palzeontologists acquiesced in their being assigned 
to the Hydrozoa, in spite of the difficulty arising from the 
formerly commonly accepted presence of the virgula or “ solid 
rod ” in the rhabdosome and the supposed floating habit of the 
graptolites. The fact that they were found to furnish excellent 
data for the detailed division into zones of the Cambrian, 
Ordovician, and Silurian strata prevented their neglect, although 
so refractory to all attempts at close morphologic investigation, 
and the search for them in the field never relaxed. The grati- 
