92 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



Walther applies his knowledge of this recent algal deposit to the examination 

 of a Tertiary " Nulliporenkalk " near Syracuse. In many parts of this forma- 

 tion there occur well-preserved specimens of Lithothamnion, but in others 

 a gradual obliteration is observed of all plant structures until the rock becomes 

 entirely structureless. A similar instance of structureless limestone is de- 

 scribed from the Lias of Todten Gebirges [Todtes Gebirge].^ 



In an interesting paper on the " Origin of the Bighorn Dolomite " '' 

 Dr. EHot Blackwelder considers the influence of calcareous algae in 

 the deposition of this Ordovician dolomite. After a very clear dis- 

 cussion he concludes that an alga of the type of the modem coralline 

 alga Lithophyllum is the most likely form to have made the struc- 

 ture that is very widely present in the dolomite. The absence of 

 microscopic cells is explained by the crystallization of the dolomite. 

 Of the branching structures he says, " It seems more likely that 

 they represent banks of calcareous algse than any of the plant-like 

 animals." ' 



One of Dr. Blackwelder's illustrations (pi. 33, fig. i) suggests a 

 form allied to Greysonia basaltica (pi. 17, fig. 2 ; pi. 18, fig. 2) of the 

 Xewland limestone. There is to me no apparent reason why the 

 Jjlue-green algse (Cyanophycese) should not have lived in the marine 

 waters in which the Big Horn dolomite was deposited and also 

 reproduced forms allied to those of the Algonkian. This comment 

 is made with the hope that a thorough search will be carried on 

 throughout the Palaeozoic group for forms resembling those of the 

 Belt series of limestones. 



Bacterial deposits. — Dr. Alfred G. Mayer in speaking of the work 

 of the late Mr. George H. Drew wrote as follows : * 



In 1910, Sanford, and also Vaughan, published the conclusion that a consider- 

 able portion of the calcareous muds in the bays and sounds of southern Florida 

 was precipitated out of the sea-water in some unknown manner. It remained 

 for Drew, in 191 1, to discover that there is in the warm surface waters of the 

 West Indian and Florida region, and especially in the limestone mud itself, a 

 bacillus which deprives the sea-water of its nitrogen, thus causing the calcium 

 to combine with the dissolved carbon dioxide and to form the finely-divided 

 limestone mud so characteristic of coral-reef regions. Drew isolated this 

 bacillus and found that it became inactive in even moderately cold water, 

 and thus it functions only in warm or tropical seas, thriving best at depths 

 of less than 100 fathoms. In the surface waters of the Bahamas and Florida 

 it is the most abimdant marine bacillus. 



' Gardiner. " The Fauna and Geography of the ]\Ialdive and Laccadive Archi- 

 pelagos," Vol. 2, pp. 10-26. 



^ Bull. Geol. Soc. America, Vol. 24, pp. 607-624, pis. 28-35. 



^ Idem, p. 624. 



■* Papers from the Tortugas Laboratory, Carnegie Institution of Washington, 

 Vol. 5, 1914, p. S. 



