40 ANNUAL REPORT OF THE 
REPORT ON INVERTEBRATE PALAEONTOLOGY. 
By Percy E. RaymMonp. 
As last year, most of my time in the Museum was devoted to 
the arrangement of the collection of trilobites. The specimens 
belonging to the Paradoxidae and Mesonacidae were studied and 
relabeled, and a paper on the ontogeny of Paradoxides written as a 
result of this study. A paper describing some of the more impor- 
tant of our extensive collection of trilobites from the Silurian of 
southeastern Wisconsin was also prepared, this paper involving 
a review of the classification of the Illaenidae. 
Miss H. 8. Clark aided in the preparation of the catalogue of a 
part of the collection of trilobites. 
About six weeks were devoted to the identification and study of 
two collections made for the Geological Survey of Canada in pre- 
vious years, the Museum receiving a set of duplicates in return 
for the identifications. As a result of this work, three papers were 
prepared which are now in press. 
Having received a grant from the income of the Shaler Memorial 
fund, for an investigation of the Ordovician and Silurian strata 
of the Baltic provinces of Russia and Sweden, I spent the greater 
part of April in preparation for this trip, and sailed for Europe on 
April 28, returning to Cambridge, September 14. On this trip 
I was accompanied for’ a part of the time by Prof. W. H. 
Twenhofel of the University of Kansas. We studied the strati- 
graphy and collected the fossils of the Cambrian, Ordovician, and 
Silurian deposits in the Governments of St. Petersburg and Es- 
thonia, and in the southern parts of Sweden and Norway. ‘This 
work yielded valuable results in regard to the stratigraphy of the 
regions studied, and in relation to the correlation of these with 
similar strata in America. Considerable collections were made, 
most of which have not yet reached Cambridge. I also saw and 
studied in part the Ordovician fossils in the principal museums of 
London, Paris, Frankfort, Berlin, St. Petersburg, Stockholm, 
Upsala, Lund, and Christiania. 
The following accessions have been received during the year:— 
