74 JOURNAL OF THE [.Iuly> 



tomaceous clays of Richmond, Virginia, in the profusion of dis- 

 coidal forms covering the surface. These forms, however, are 

 but spectral, as they vanish on wetting. The nodule, rubbed 

 down in water with a brush, will leave a sandy sediment contain- 

 ing sponge spicules, polished sand grains, ovoid amber-like grains, 

 and species of disc forms of the following genera : Coscinodiscus, 

 Actinopktychus, Actinocydits, Triceratiitm^ and minute plates show- 

 ing a plexus of Me/osira and Rap/ioiieis, the diatoms having been 

 metamorphosed in such manner as to be soluble in nitiic or 

 other acids, the same as the organic phosphatized remains of the 

 vertebrates associated with the clay. Finally, the clay may be 

 thoroughly disintegrated by boiling in strong soap solution, and 

 after standing for ten hours it will be reduced to a homogeneous 

 sediment, readily washed and cleaned for examination. 



'' Concentration of the diatoms from the sand is very difficult, 

 on account of the similarity of the specific gravity of the diatoms 

 and of the sand and other grains associated therewith. Acid 

 treatment, being in this case impracticable, must be avoided. 

 The material is adapted for selected or for strewn mounts. In 

 the latter method a few of the prevailing species may be studied 

 with interest and satisfaction, thereby affording something novel 

 in the marine fossil diatomaceous line of research apparently not 

 heretofore recorded." 



Dr. Carl Heitzmann addressed the Society on " Nerves and 

 Nerve Action." This address was illustrated by exhibits, as 

 noted below, and an abstract of the address is published in this 

 number of the Journal, page 66. 



OBJECTS EXHIBITED. 



1. Diatomacien genus-platte. Trice7-atii(m trhmcria, 280 

 forms, prepared by E. Thum, Germany : by Henry C. Ben- 

 nett. 



2. Mouth-parts of Tapeworm : by L. Schoney. 



3. Photomicrograph of Navicula crassinervis (Spencer ^) : by 



H. G. PiFFARD. 



4. Motor ganglion of spinal cord of child. 



5. Transverse section of gray substance of spinal cord of rab- 

 bit. 



