38 JOURNAL OF THE [January, 



slides to illustrate some of the features connected with this 

 special deposit. On two slides I show selected rhizopods, to be 

 viewed strictly by polarized light; and two slides of deposit 

 strewn so as to show the various associated micro-organisms by 

 polarized light. These slides have no cover glasses, but are 

 covered by a thin film of mica, with the object of intensifying 

 the brilliancy of the prismatic effects. Under this arrangement 

 we are provided with a kaleidoscopic effect of color, produced 

 by the polarized light when the polarizing prism is revolved. 



" I have also sent two vials, one containing the rhizopod, fora- 

 minifera, and mica material, the other containing the marine and 

 fresh-water diatoms, concentrated from the mud already alluded 

 to. The diatoms are a water-washed concentration by Dr. 

 Geo. H. Taylor, of Mobile, without use of acids. He is now 

 •engaged on the reduction of a large bucketful of the deposit 

 to the same state as that shown by the slide of diatoms pre- 

 pared from the material in the vial sent herewith. The diatoms 

 indicate an aggregation of about fifty marine and fresh-water 

 species — Actinocydus Ehrenbergii, Cainpylodiscus crebrosus, Nitzs- 

 €hia circumsuta, and Terpsinoe musica. Another interesting fea- 

 ture is that Triceratiwn favus is absolutely absent, and that 

 Cymatopleura elliptica and a pretty Acanthes are seen in every 

 slide of the material, while they are almost unknown as occur- 

 ring in all previous gatherings tributary to Mobile until this 

 locality was casually met." 



OBJECTS EXHIBITED. 



1. Vanadamite from Arizona: by E. C. Bolles. 



2. Percylite from Arizona, together with a large series of 

 minerals in minute paper boxes : by E. C. Bolles. 



3. Rhizopods from marsh mud, Mobile River, Alabama, pre- 

 pared and donated by K. M. Cunningham: by J. L. Zabriskie. 



4. A slug-like form of aquatic life: by Stephen Helm. 



5. An undescribed form of aquatic life, formerly exhibited as 

 No. 4: by Stephen Helm. 



6. An undescribed form of aquatic life resembling Cordylo- 

 phora lacustris: by Stephen Helm; 



7. Hydra viridis: by Stephen Helm. 



3. Young Hydro-medusae, living: by L. Riederer. 



