312 



FRESH-WATER BIOLOGY 



39 (40) Terminal spines of longer gemmule spicules with a simple curve. 



Asteromeyenia plumosa (Weltner) 1895. 



Sponge massive, though brittle and friable. 

 Skeleton spicules slender, smooth, sharply pointed 

 at both ends, nearly straight. Shaft of long birot- 

 ulates almost smooth, slender, straight; rotules 

 a circle of curved hooks, joined at the base. 

 Short birotulates with stouter shafts, profusely, 

 irregularly, and strongly spined; rotules not mark- 

 edly convex in profile, irregularly, narrowly, and 

 deeply serrated. Free spicules very minute, 

 abundant, resembling those of Dosilia. Gem- 

 mules large, spherical, with single, very small 

 aperture having short, straight foraminal tubule. 

 From Pinto Creek, Kinney County, Tex., and 

 Shreveport, La.; one specimen measured 29 X 

 25 cm. 



Fig. 575. Asteromyenia plumosa. ^ , gemmule show- 

 ing aperture in center, X 35 ; ^. short birotulates, X 1 20; 

 C, long birotulates, X 120; Z), free microscleres. X 120; 

 £, skeleton spicule, X 120. (After Annandale.) 



40 (39) Terminal spines of longer gemmule spicules distinctly recurved. 



Asteromeyenia radiospiculata (Mills) if 



Resembles A. plumosa. In profile the rays of the longer 

 gemmule spicule have almost the form of a J. Ohio and Illi- 

 nois. At Granite City, 111., specimens were taken from settling 

 tanks of the city water works, measuring 42 x 12x8 cm. 



Fig. 576. 

 mount.) 



Spicules ot Asteromeyenia radiospiculata. X 100. (From 



41 (38) Dermal spicules acerate if present. 



Heteromeyenia Potts . .42 



SpongilHdae producing gemmules with birotulate spicules of two distinct classes, long and 

 short. Margins of rotules not smooth but dentate or incised. 



42 (43) Rotules of gemmule spicules of smaller class finely serrated. 



Heteromeyenia ryderi Potts 



.2. 



Sponge massive, often hemispherical. Gemmules numerous, crust 

 thick, foramina short and inconspicuous. Skeleton spicules grad- 

 ually pointed, entirely spined except at the tips. Dermal spicules 

 wanting. Shafts of long birotulates spined, rotules of three to six 

 short recurved hooks, sometimes umbonate. Rotules of small birot- 

 ulates nearly as great in diameter as the length of their shafts. 

 Shafts smooth or with few spines. Shallow flowing water, Florida 

 to Nova Scotia, and inland at least as far as Iowa. 



Fig. 577. Spicules of Heteromeyenia ryderi. Four types of spicules 

 figured here: skeleton spicule; long gemmule birotulates. hooked and 

 spined; short birotulates; surface of rotules, margins lacinulate, surface 

 microspined or granulated; spherical amorphous spicule. X loo. (After 

 Potts.) 



43 (42) Rotules of gemmule spicules of small class coarsely serrate. 



44 



