CYCLAS. 



The recent species of Cyclas are peculiar to the nor- 

 thern hemisphere, and we believe are only found in the 

 European and North American continents, they abound 

 in ditches, ponds, slow streams and lakes, their little 

 animals move about in the water with facility by the use 

 of a flexible muscular foot, with which they appear to 

 take hold of any substance within their reach and draw 

 themselves toward it.* 



Such as occur in a fossil state appear only to belong 

 to the most recent lacustrine formations, they are pro- 

 bably post diluvian and belong to the same species as are 

 found living at the present time. 



Several recent species occur in Britain, and some 

 attempts have been made to divide them into several 

 genera, we do not think such divisions necessary, particu- 

 larly when it is considered that there are not many species 

 and that the differences are but slight. 



We have represented Cyclas rivicola. 



* We had nearly forgotten to mention that most if not all the Cyclades 

 are viviparous, i. e. that their young are completely formed before they are 

 expelled from the ovary. 



