124 PROCEEDINGS OF THE ACADEMY OF 



The death of Dr. A. A. Henderson, U. S. N., of Dr. P. R. Ban- 

 nan, U. S. N., members, and John Edward Gray, correspondent, 

 was announced. 



April 13. 



The President, Dr. Ruschenberger, in the chair. 



Ten members present. 



The following paper was presented for publication : " Synopsis 

 of the Geomyidoe." By Dr. Elliott Coues, U. S. A. 



April 20. 



The President, Dr. Ruschenberger, in the chair. 



Twenty-four members present. 



The following paper was presented for publication : "Descrip- 

 tions of a new Fossil Ostrea from the Amazon." By T. A. Conrad. 



On a Curious Rhizopod. Prof. Leidy remarked that in some 

 water with aquatic plants, from Absecom Pond, N. J., preserved in 

 an aquarium during the winter, he had detected a remarkable rhi- 

 zopod, which he thought might best be compared to the reticular 

 pseudopods of a Gromia separated from the body. The creature 

 moved actively and assumed the most varied forms. At one time 

 it appears as a C}dinder or a ball of jelly which may spread itself 

 into a disk of extreme thinness, from the edge of which emanate a 

 multitude of delicate pseudopods minutely ramifying, and with the 

 contiguous branches anastomosing, as in the extension of the net 

 of a Gromia. At other times the creature divides up into branches 

 from a trunk in the manner of a tree, but with the contiguous 

 brandies anastomosing. At times also the animal assumes the 

 form of a cord, and the jelly accumulating along some portion of 

 it will then move along the apparent cord like a drop of water run- 

 ning down a piece of twine. The branching pseudopods extending 

 into a net, the large angular meshes gradually contract by the widen- 

 ing of the cords, so that the meshes become perfectly circular and 

 .appear like vacuoles imbedded in the jelly. A circulation of jelly 

 with granules is observed along all the pseudopoclal filaments ex- 

 actly as in Gromia. No trace of a nucleus or investing membrane 

 in any position could be detected, but the protoplasmic structure 

 contained a multitude of minute vacuoles. Most of the speci- 

 mens contained no food, and only one of the largest was observed 

 to contain numerous minute Closteria. 



