14 



Brebissonia. 

 Amphipleura. 



Gyrosigiiia. 

 Scoliopleura. 



Goniphoiiema. 

 Rhoicospheni ia. 



hh. Raphe bordered by two ridges, 

 i. Central nodule small or only slightly elongated, 

 ii. Central nodule much elongated, rib like, 

 gg. Raphe strongly sigmoid, 

 h. Cell not twisted (fig. 23). 

 hh. Cell twisted. 



ff. Rachis of valve with a keel ; keel (including raphe) sigmoid, 

 median. Amphiprora. 



ee. Valves not parallel, 

 f. Ends of valves approximating, 

 g. Cells straight in girdle view (iigs. 29, 30). 

 gg. Cells curved in girdle view, 

 ff. Edges of valves approximating, 

 g. Valves without transverse ribs, 

 h. Girdle narrow, not striate (fig. 33). Cynnbella. 



hh. Girdle broad, striate (fig. 41). Amphora. 



gg. Valves with transverse ribs, raphe not evident, (fig. 35). 



{Cystopleura) Epitheinia. 

 dd. Rachis lateral, less often median, punctate keeled, raphe not plainly 

 visible. 

 e. Keel median. . Bacillaria. 



ee. Keel at one edge (figs. 19, 20). [=^ Hoinoeocladia) Nitzchia. 



cc. Rachis evident as a narrow, unmarked strip or keeled ; valve with two 

 lateral wing keels, each enclosing a raphe, 

 d. Valve surface undulate. {^^Cyntatoplcura) Spliinctocystis. 



dd. Valve surface not undulate, 

 e. Valve cuneate, reniform, elliptical or linear (fig. 38). Surirella. 



ee. Valves .sub circular, saddle shaped (figs. 31, 32). Campylodiscus. 



PROTOZOA. 



a. Animals with tentacles, and when adult usualh* attached by a stalk. 



SUCTORIA, 



aa. Animals with pseudopods, flagella, or cilia. 



b. Animals with pseudopodia. 



c. Pseudopods flexible. Amoeba (fig. 5), Arcella (figs. 3, 4), Difilugia 



(fig. 6). E.HIZOPODA. 



cc. Pseudopods rigid. HELIOZOA. 



bb. Animals with cilia or flagella. 



c. Animals with cilia. Paramcecium, etc. CILIATA. 



cc. Animals with i or 2, rarely more, long flagella. MASTIGOPHORA. 



To the Mastigophora belongs a large numlier of forms, many of which 



by botanists are grouped with Algae. The green colonial forms, P'o/iv^r, 



Eudorma, Pandoritia, Slephanosphcrni, Gonium, Chlamydomonas, Sphcer- 



ella, and the brown or colorless genera Peridinium, Ceratiuvi, Ditiobryon, 



Urcglena, and Synura have already been included in the foregoing keys. 



Among the numerous forms which may be encountered, are Carteria (fig. 



i) w'ith four flagella; MaUo))ionas (fig. 12) with am1)er colored chromato- 



