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FRESH-WATER BIOLOGY 



11 (10) Dermal spicules acerate Spongilla wagneri Potts 1889. 



Gemmules abundant. Skeleton spicules long, robust, smooth. Dermal spicules very 

 numerous. Gemmule spicules spined, long, curved. Spines most numerous at extremities. 

 Recorded only from brackish water of southwestern Florida. 



No figure yet published. 



12 (i) Gemmule spicules of birotulate type, more or less modified. 



Sub-family MEYENINAE Vejdovsky . . 13 



13 (47) Apertures of gemmules not provided with filamentous appendages 14 

 14(46) Rotules of gemmule biro tulates nearly equal 15 



1 5 (37) Gemmule birotulates of a single class. '.-., 16 



1 6 (19) Margins of rotules entire, i.e., smooth, not serrate. 



Trochospongitta Vejdovsky . . 17 



17 (18) Skeleton spicules smooth. . Trochospongilla leidyi (Bowerbank) 1863. 



Sponge of a peculiar light gray or drab color, encrusting thin, persistent. Gemmules numer- 

 ous, each surrounded by a capsule of skeleton spicules. Skeleton spicules short, smooth, 

 robust. Dermal spicules wanting. Gemmule spicules short, birotulate, margins entire and 

 exflected. From Louisiana as well as original field of discovery near Philadelphia. Generally 

 distributed in the Illinois River from the mouth to La Salle according to F. Smith. 



FIG. 565. Trochospongilla leidyi. A. Upper surface of portion of a layer of gemmules, each of which is 

 surrounded by a lattice capsule (c) of spicules resembling those of the skeleton; at the summit an open 

 space around the foraminal aperture (a), more than one being sometimes present. X 50. B. Four types 

 of spicules figured here: smooth skeleton spicules, abruptly pointed; same, with rounded terminations; 

 short birotulates with entire margins; same with rotule twisted or exflected; face of rotule; group of 

 rotules as they appear upon the surface of the gemmules. X 100. (After Potts.) 



18 (17) Skeleton spicules strongly spined. 



Trochospongilla horrida (Weltner) 1893. 



Sponge encrusting, white, gray, yellow, or brown. 

 No gemmule spicules except birotulates which are 

 smooth-margined, low, small. Lives in standing or 

 flowing water. Rare. F. Smith found one specimen 

 each in the Illinois River near Starved Rock and in the 

 Big Muddy River in southern Illinois. 



FIG. 566. Trochospongilla horrida. Spinous skeleton spic- 

 ules. X 180. Birotulate gemmule spicules. X4oo. (After 

 W. Kukenthal.) 



