FRESH WATER SPONGES OF NOVA SCOTIA—~MACKAY. 239 
spicuously fusiform or largest at the centre, where are found one 
or more long spines. Their rotules consist. of three to six irregu- 
Jarly placed rays, recurved at the extremities. 
Birotules of the shorter class abundant, and compactly placed, 
around the statoblasts; shafts mostly smooth, though sometimes 
bearing a single spine; irregularly cyndrical, but rapidly widen- 
ing to support the rotules, which are large, umbonate, nearly flat, 
and finely lacinulate at their margins; occasionally bearing 
spines. 
Measwrements—Skeleton spicules 0.0075 inch long, by 0.00075. 
inch thick; length of long birotulates 0.0021 inch; of short bi- 
rotulates 0.0012 inch; diameter of dise of latter, 0.0009 iach. 
The above description is substantially that of Mr. Potts, who 
described the species before the Philadelphia Academy of Natural 
Sciences, at its neeting of February 24th, 1885. 
This most beautiful of all our sponges was originally found in 
the lakes of the watershed of the Provinee, between Pictou, 
Guysboro’ and Antigonish, August, 1884. It has since been 
observed in the lakes and streams of Halifax County. 

HETEROMEYNIA PICTOVENSIS, Potts. 
A.—Skeleton spicules. 
B.—Long birotulate. 
©.—Short birotulate. 
