No. 1712 



FRESH WATER SPONGES— ANNANDALE. 



405 



HETEROMEYENIA PLUMOSA Weltner (Potts MS.)- 

 Heteromeyenia plumosa Weltner, Archiv fiir Naturgesch., 1895, part 1, p. 127. 



Specimens from the U. S. National Museum are labeled ''These are 

 fragments of a single specimen 3 inches in diameter." Weltner, who 

 examined similar specimens, gives a short comparative description, 

 noting those characters in which the form differs from //. radiospicu- 

 lata Mills. As Mr. Potts apparently no longer intends to describe 

 H. plumosa it ma^^ be as well to give a fuller description. 



E.X240 



D. X240 



C.X240. 



Fig. 3.— Gemmule and spicules of Heteromeyenia plumosa. A. Gemmule, x 70, showing aper- 

 ture IN CENTER. B. Short birotulates, x 240. C. Long birotulates, x 240. D. Free micro- 

 scleres, X 240. E. Skeleton spicule, X 240. 



The sponge appears to have been rather massive, although very 

 brittle and friable. The radiating fibers, which have an obhque 

 course, and some of the transverse ones, are easily visible to the 

 naked eye. The color (dry) is a sooty black in the external parts, 

 but becomes paler toward the base. 



A vertical section examined under the microscope shows that the 

 radiating fibers, although not very slender, are loosely compacted. 

 Apparently little if any spongin is present. 



