TETHYS CERVINA DALL AND SIMPSON 57 



and doubtless contribute to the well known characteristic de- 

 fensive secretion of these animals. 



CIRCULATORY, EXCRETORY AND RESPIRATORY SYSTEMS. 



The circulatory, excretory and respiratory systems of Tethys 

 cenrina, so far as studied, were not found to differ markedly from 

 those of other species, and matters of familiar knowledge, and 

 hence they will not be entered upon in this place. 



Leland Stanford Junior Zoological Museum, Invertebrate 

 Series No. 144. 



