542 Wisconsin Academy of Sciencesy ArtSy and Letters. 
The mastax is very aberrant; the trophi, which normally seize 
and subdivide the food, are virtually atrophied and their func¬ 
tions transferred to a pair of hooked ‘ ‘ pseudunci ’ probably a 
highly specialized form of the epipharynx; no gastric glands are 
present, but the walls of the stomach are produced into a number 
of gastric caeca and contain symbiotic zoochlorellae. 
No retrocerebral organ is present; the ganglion is small and 
the eyespot at its posterior margin. 
Type of the genus.—Birgea enantia Harring and Myers. 
