MICROSCOPIC FORMS FOUND IN TUE CROTON ^VATER. 11 



Podocystisii aiuericana, B. 



# (Plate, Pig. 38.) 



Lorica nearly sessile ; bases obovate, with a longitudinal line through the middle, 

 and numerous granules arranged in double rows, producing more or less regular 

 transverse bars. The side view is wedge-shaped. Length, juVijth of an inch, 

 — 4™. 



This very pretty species is not uncommon as a parasite upon filamentous Algae 

 in Long Island Sound, and at Greenport, New York. 



Telra gramma amcricana, K- (Seo page 7.) 

 Toxariuiu undiilatiiiii, B. (See page 15.) 

 Triccratium setigerum, B. 



(Pl.vte, Fig. 24.) 



Bases triangular, slightly convex with rounded edges, and bearing three large 

 obtuse projections, or horns, at the base of each of which is placed a setiform pro- 

 cess. Sides rectangular or square, separated from the ends by deep constrictions. 

 The whole surface covered with granules arranged in a decussate manner. Length 

 from base to base, 6°". Width of sides, 3". to 4". 



This very beautiful species occurs at Ballast Point, Tampa Bay, Florida, Avhere 

 it is not rare. It appears to be allied to the Triceratium spinosum, B., which I 

 found fossil at Petersburg, Virginia. (See London Pliysiologkal Journal, I. 143. 



Zygoceros circinus, B. 



(Plate, Figs. 19, 20.) 



Bases elliptical, terminating in truncated cones without horns, but having two 

 Jong, setiform, bent spines. Sides, minutely and decussately punctate. The de- 

 cussating rows of granules are omitted in the figure. 



Fossil at Richmond, Virginia. 



Zygoccros ? radiatus, B. 



(Plate, Fig. 29.) 



Base with an elliptical outline; horns slightly elevated, minutely punctate; 

 basal surf\xce covered with radiating and dichotomous rows of granules ; sides not 

 yet seen. Length of base about 7"". of an inch. Width about 4"". 



Although I have only seen a few of the bases of this elegant species, I have lit- 

 tle doubt "that it is a congener of Zijrjoceros rhombus, Ehr. Its large size and beau- 

 tiful markings make it a very interesting species. I found it among Algae from 

 Halifax, Nova Scotia. 



VIL 



On the Microscopic Forms Found in the Croton Water in New York City. 



It has long been known to the New York microscopists, but not to the public 

 generally, that the Croton water aboiuids in beautiful microscopic organisms, and 

 particularly in Diatomaceae and Desmidieae. The following list gives the names 



