DES MOINES ACADEMY OF SCIENCE. 



exercised in the interests of his special science lest a greater injustice be done 

 the student who shall follow him. 



Bibliographic matter would be inappropriate in a paper of this character, and 

 but little such matter has been admitted. ' A simple reference to a figure of each 

 form where one is known to exist, in most cases the original has been deemed 

 useful. In general, descriptions will be found in connection with the plates in- 

 dicated in the several references. 



