184 Miscellaneous. 



end than the other ; the inner border gently convex and entire ; 

 the outer border is marked by six shallow notches, which are sepa- 

 rated by as many sharp compressed projections. The emarginations 

 and denticles are the termini of corresponding grooves and ridges, 

 which radiate from a smooth space along the inner margin of the 

 crown. From this plane the grooves gradually deepen to the margin ; 

 the separating ridges are acute, and without irregularity or serration. 

 The base or root of the tooth is quite wide ; externally it extends 

 beyond the border of the crown at the notches, and has projections 

 corresponding to the denticles, from which it is separated by a hori- 

 zontal notch. On the inner side the base extends like a shelf beyond 

 the posterior half of the crown, and is produced backwards beyond 

 its posterior border. The inferior plane is concave in transverse 

 section ; the crown is plane in all directions. 



metre. 



Length of crown preserved -021 



Width of crown -OlS 



Length of root preserved '022 



Depth of tooth internally -005 



„ externally •003 



This Ceratodus resembles the species described by Agassiz under 

 the names of C parvus and C. serratus from the English Trias, but 

 differs from them in the shortness of the tooth-like processes. In 

 none of the described species do I find such a development of the 

 basis on the inner side. 



This species is of interest as introducing the genus to North 

 America. It is dedicated to Dr. Winslow, to whom we are indebted 

 for its discovery. — Proc. Acad. Nat. Sci. PhUadelphia, September 28, 

 1875. 



Formation of Nitrites by Bacteria. 



The presence of nitrites in spring- waters, which has usually been 

 ascribed to the oxidation of ammonia therein, is now stated by 

 Meusel to be produced by the reduction of nitrates by the agency of 

 Bacteria. In proof of this he shows : — that such water which con- 

 tained Bacteria and nitrates, but neither ammonia nor nitrites, gave 

 after standing four days the reactions of nitrous acid ; that anti- 

 septics, such as salicj^lic acid, phenol, benzoic acid, alum, and much 

 salt even, prevent or hinder the production of nitrites ; that aque- 

 duct-water containing pure nitrates, which alone does not show 

 the production of nitrites even in presence of Bacteria, has this 

 change effected upon the addition of glucose, gum, dextrin, cellulose, 

 starch, &c., in the course of from two to fourteen days ; that freshly 

 distilled water, boiled with glucose and nitre, shows no nitrites even 

 after standing for weeks, because Bacteria are absent ; and that 

 putrefying albuminates reduce nitrates to nitrites. The decomposi- 

 tion of cellulose by Bacteria in presence of nitrates proves that nitre 

 is not only direct food for plants, but that it also performs by its 

 oxygen an important function in the soil. The author believes that 

 these facts have important bearings in agriculture and in medir-ine. 

 — SiJlimans American Journal, January 1876. 



