When mucking about in your local vernal pool looking for salamanders and other slimy things, look for little clams swimming about in the water column.  There should also be a bunch of little white clams on the bottom in the leaf litter, these are pill clams and are the subject for later blogs. The Clam Shrimp are transparent as shown above and swim around mostly in late summer.  A key feature is the presence or absence of rings on the shell or carapace.  If the ones you are looking at have rings, they fall into two species, both are State-listed Rare Species: Eulimnadia agassizii or Limnadia lenticularis.  If the carapace is smooth, it is Lynceus brachyurus.

Drawing above from Doug Smith’s “Keys to the Freshwater Macroinvertebrates of Massachusetts”, used with permission from Doug.

Leo Kenney offers us a peek at Limnadia lenticularis.