The object of the author in this paper is to prove the importance of examining, in the living and expanded state, all soft, collapsible, and contractile animals. He describes in detail the anatomy of the genus Clio, illustrating his description by a drawing. He points out the confusion that has occurred in systematic works between the species named respectively Clio borealis and Clio australis; and he describes characters by which he thinks that these two species ought to be separated from Clio caudata and erected into a new genus; which, however, he declines to designate, being averse to add new names to a list already large.