Fig. 14. Invertebrate life on a boulder measuring 6 x 4Vo * '^/2 inches, 

 water 20 inches deep. The characteristic animals are the snail (Gonio- 

 basis, 1) ; the beetle larva (Psephenus, 2) ; the spiral caddis-fly (Heli- 

 copsi/clie, 3) , and the May-fly larva (Heptayenia, 4) . Short Point. Lower 

 South Bav. 



