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BULLETIN OF THE BUREAU OF FISHERIES 
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Ccelenterata 329 
Porifera 329 
Cnidaria 330 
Hydrozoa 330 
Hydromeduste 330 
Scyphomedusse 331 
Anthozoa 332 
Ctenophora 333 
Vermes 334 
Nemathelminthes 334 
Nematoda 334 
Chaetognatha 334 
Bryozoa 339 
Annelida 340 
Arthropoda 346 
Crustacea 346 
Copepoda 346 
Cirripedia. 349 
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Arthropoda— Continued. 
Crustacea— Continued. 
Amphipoda 350 
Isopoda 352 
Schizopoda 352 
Stomatopoda 354 
Cumacea 354 
Decapoda 355 
Arachnoidea 364 
Mollusca 365 
Echinodermata 365 
Chordata 366 
Hemichordata 366 
Urochordata 367 
Cephalochordata 367 
Vertebrata 367 
Conclusions 367 
Bibliography 373 
INTRODUCTION 
One object of this biological survey of Chesapeake Bay has been to make collec- 
tions and identifications of various animals and plants found there in order to learn 
more of their distribution and abundance. An equally important object has been to 
record at the same time some of the environmental conditions which might determine 
such distribution and abundance. In addition to this it has been the intention of the 
survey to continue the work for several years in an effort to ascertain what the usual 
environmental conditions in the bay are, so that when great mortality of fishes, oysters, 
crabs, clams, etc., occurs there will be data at hand from which to decide as to what 
unusual changes may have been the cause of the trouble. Finally, it has been hoped 
that the information obtained concerning salinity, temperature, and plankton content 
of the water may help at some time in the future to throw light on the laws which 
govern the migration of fishes, crabs, and other organisms in Chesapeake Bay. 
The survey has been a rather general one, many regions having been visited at 
intervals, so that no one region has been studied intensively — daily for example — 
although each region has been visited several times during a year. At certain ones, 
observations and collections have been made every 1 hours for a period of 24 hours. 
The temperature and salinity data obtained during several years of observation have 
been studied. An attempt has been made to work out the distribution of the plankton 
diatoms and other forms and also to see how they are related to salinity and tempera- 
ture; but the role played by each of these factors can not be conclusively shown, 
owing to the difficulty of controlling the numerous factors involved. In order to have 
a better idea of the general physical characteristics of Chesapeake Bay before taking 
up the discussion of salinity, temperature, and diatom distribution, the following 
section on the physical features has been included. 
PHYSICAL FEATURES 
Chesapeake Bay is a large estuary on the eastern coast of the United States lying 
between latitude 76° to 76° 30' and longitude 37° to 39° 30'. It forms a deep inden- 
tation into the States of Maryland and Virginia, extending inland about 160 nautical 
