PLANKTON OF THE GULF OF MAINE 
347 
The large Staurophora no doubt takes a very heavy toll of Calanus and smaller 
copepods, which are often to be found entangled along the elongated lips of its cruci- 
Fig. 96. — Occurrence of the hydromedusa Staurophora mertensii. X, locality records, summer of 1912; ®, subsequent 
years. The hatched curve includes its chief zone of occurrence within the Gulf of Maine 
form mouth opening, and since the young Staurophora also feed on them greedily 
according to Hartlaub (1899), this medusa must play an important role in the natural 
economy of the animal plankton wherever it is plentiful. 
