238 FRESH WATER SPONGES OF NOVA SCOTIA— MACKAY. 
ly known is a lake on Mount Everett, Berkeshire Co., Mass., 
U.S. A., 1800 or 2000 feet above the sea. The flesh spicules of 
this species have been observed in the diatomaceous deposits of 
the lakes which supply the city of Halifax with water. (See 
slides 28, 29 and 30). 
senus IJ]].—HETEROMEYENIA. 
Statoblast birotules of two orders, one long, the other short. 
6. H. Ryderi, Potts. 
Rather massive with lobular protuberances. Long birotules, 
with scattered spines on shaft and few incurved, nearly barb- 
like, rays. Short birotules, with small shaft enlarging towards 
the large finely-toothed dises. (For structure and spiculation 
see slides 31, 32 and 33). Very abundant in MacKay’s Lake, 
Pictou Co. 
7. H. argyrosperma, Ports. 
Sessile, encrusting. Large birotules more than twice the size 
of those of H. Ryderi, rays more hook-like. Small birotules 
about half the length ; few rays irregularly hooked ; shaft with 
stout scattered spines. In Garden of Eden Lake, Pictou Cu., 
and adjacent lakes. 
8. H. Pictovensis, Ports. 
Sponge light green, massive, encrusting; texture very com- 
pact; spicules non-fasciculated, persistent; surface mostly smooth 
and firm to the touch. Statoblasts very scarce, spherical; erust 
thick. 
Skeleton spicules cylindrical, short, robust, rounded or abruptly 
terminated ; entirely spined,—spines conical at the centre of the 
spicule, elsewhere generally curving towards each extremity; 
rounded terminations of spicules covered with short spines, 
though frequently a single large spine or acute termination is 
seen at one or both extremities. 
Birotulates of the longer class surrounding the statoblasts, 
rather numerous, one-half longer than the others; shafts con- 
