THE SPONGES (PORIFERA) 



313 



44 (45) Rotules of gemmule spicules of small class regular mushroom-shaped, 

 shafts usually smooth. . Heteromeyeniarepens Potts iSSo. 



Sponge encrusting, thin. Gemmules not abundant. Skeleton 

 spicules rather slender, sparsely microspined, gradually pointed 

 Dermal spicules nearly straight, entirely spined. Gemmule birotu- 

 lates of longer class comparatively few; shafts, smooth or with one 

 or a few conspicuous spines often irregularly bent. Rotules dome- 

 shaped, rays incurved like fish hooks. Small birotulates very nu- 

 merous, about two-thirds the length of the large ones Quiet 

 almost stagnant water, New Jersey, Pennsylvania, and Michigan. ' 



Fig 578. Spicules of E eteromeyenia repens. Five types of spicules 

 figured here: microspined skeleton spicules; gemmule birotulates of the 

 longer class, with recurved hooked rays; birotulates of the shorter class 

 with less pronounced rays; rotules of same; small dermal spicules, coarsely 

 spined; amorphous spicule. X 100. (After Potts ) 



45 (44) Rotules of gemmule spicules of small class very irregular, shafts 

 abundantly spined. Heieromeyenia argyrosperma Potts 1880. 



Sponge minute, encrusting, gray. Gemmules abundant and 

 large. Foraminal tubules somewhat prolonged. Skeleton spicules 

 rather slender, cylindrical, abruptly pointed, sparsely spined 

 Dermal spicules apparently wanting. Shafts of long birotulates 

 sparsely spined. Rays of rotules few, long, stout, and clawlike 

 Short birotulates much smaller, abundantly spined. From Penn- 

 sylvania, New Jersey, New England States, and Nova Scotia 

 Found by F. Smith at Douglas Lake, Mich. 



Fig. 57g. Spicules of H eteromeyenia argyrosperma. Three types of 

 spicules figured here: sparsely microspined skeleton spicules; gemmule 

 birotulates of the longer class with one to three hooked rays; spined birot- 

 ulates of the shorter class. X 100. (After Potts.) 



46 (14) Rotules of gemmule spicules unequal, the proximal being larger. 



Tubella Carter. 

 Only North American species known. 



Tubella pennsylvanica Potts 1882. 



Sponge minute, encrusting, on stones or timbers in shallow water. 

 Gemmules very numerous, small. Skeleton spicules very variable 

 in length and curvature, entirely spined; spines large, conical. Der- 

 mal spicules wanting. Birotulates of gemmules numerous with a 

 large rotule next to the coat and a small distal rotule, varying from 

 the diameter of the shaft to that of the pro.^imal rotule. Margin of 

 large rotule usually entire but margin of small often angular and 

 notched. Shaft smooth. Averse to light and found as a rule under 

 stones and roots. Eastern United States generally. Found by F 

 Smith at Rhinelander, Wis., and Douglas Lake, Mich. 



Fig. 580. Spicules of Tubella pennsylvanica. Two types of spicuks 

 figured here: spined skeleton spicules; gemmule "inaequibirotulates." or 

 trumpet-shaped spicules; group of rotules seen from above, showing the 

 relative sizes of the rotules; surface of single large rotule. X loo. (.•\fter 

 Potts.) 



47 (13) Apertures of gemmules prolonged and divided into filamentous ap- 

 pendages Carter ins Potts . . 4S 



Gemmules possess a long foraminal tubule, the outer end of which carries an irregularly 

 lobed disc or is provided with long filaments. Not recognized as a separate genus by some 

 recent authors (see Annandale, 1909), but distributed among the preceding genera. 



