

380 THE AMERICAN NATURALIST. | [Vor. XXXVI. 
found bearing out our assumption that they are an intermediate 
group of animals related on one hand with the arthropods and 
on the other with the vertebrates. My plan was to study all 
the most important collections in Great Britain and the Conti- 
nent and to purchase or collect material that might be used 
for detailed study by sectioning or by other methods, as the 

Fic, 1.— l i f th fada oe the hk 
iin 39 di 
specimens and casia in ipee hts d and the ime Academy, at St. Peters- 
burg, and in the Dartmouth College Collect 

d of Bs secon eso Bares 

valuable type specimens permanently preserved in museums 
could not be utilized in this manner. 
It did not take long to discover that the following out of the 
second part of my program, the collection of Thyestes and of 
Tremataspis, was a most difficult task. So far as I know, every 
fragment of these two genera has been taken from a shallow 
pit about four feet deep and covering perhaps an area of three 
or four hundred square yards, hidden in the heart of the remote 
and otherwise little-known island of Osel in the Baltic Sea. 

