1900] MICROSCOPICAL JOURNAL. 187 



water diatoms, Valleys of Tombigby and Alabama rivers 

 and Mobile Bay," thus making a broad inference to cover 

 the probable source or origin of the newly found deposit. 



Before this suggestion had reached me, I had settled 

 on the theory that the deposit was the result of submer- 

 gence of a marine salt-water marsh, as there are in it 

 myriads of Foraminifera, Rhizopods, Sponge spicules, lig- 

 nitized-wood fragments, pine pollen, fern spores, and 

 many kinds of vegetal tissues. The remarkable occurrence 

 of some eight species of Pleurosigma, therein indicated 

 the analogue of the recent salt water marshes of the Con- 

 necticut shore, so fully reported on by Mr. Wm. A. Terry 

 in former numbers of this Journal. 



For years past I have sought in vain for superficial water 

 bodies near salt water, along the Gulf coast, giving indi- 

 cations of Pleurosigma, and it is only in the deposit now 

 on record, that they were found in characteristic num- 

 bers and quantity for the first time. Thus, at the close 

 of twenty-two years I have practically studied, and dis- 

 tributed at large, all that is of interest to the pursuit and 

 study of the diatoms for this region. 



This particular deposit fills the missing link that I had 

 hoped for in the fall of 1888, at which time I prepared a 

 type-slide of all species then available in the territory 

 contiguous to Mobile. That slide was referred to in an 

 article contributed by myself and printed in "The Micro- 

 scope," April, 1889, and now we are offered a chance to 

 contrast the newly found deposit, with an old slide con- 

 taining an aggregation of more than 1,500 separate dia- 

 toms. 



The type slide as studied by J. D. Cox, showed some 90 

 species and varieties ; as a result of working on fresh- 

 water, and salt-water diatom sources, such as bay, river, 

 pond, creek, lake, bayou, marsh, and swamp; all of the 

 above sources merely providing recent species. In three 

 crude study-slides submitted to Wm. A. Terry, he casu- 



