SILICIOUS AND HORNY SPONGES WILSON. 477 



Radial main fibers terminate in the conuli (pi. 44, fig. 1, from a sec- 

 tion vertical to the surface). Between these, connectives are richly 

 developed. The radial main fibers are about 2 mm. apart in the pe- 

 ripheral sponge body; fascicular and generally 300-500 \i thick; com- 

 posed of a close reticulum of slender individual fibers, the latter 50- 

 85 [j. thick and completely filled with foreign particles, chiefly sand. 



Connectives mostly 70-85 n thick; thicker ones are sometime- 

 formed by the lengthwise fusion of slender fibers; connectives in gen- 

 eral completely filled with foreign particles, chiefly sand, but not in- 

 frequently considerable spongin shows round the sand core. The con- 

 nectives extending between two adjacent radial fibers establish coarse 

 reticula, meshes mostly 300 jjl to 1 mm. wide, but the range is from less 

 than 300 [x to 2.5 mm.; the very large meshes lie between connectives 

 which are simple, that is, unbranched or only slightly branched. 

 When this skeletal arrangement is cut transversely, as in sections 

 parallel to the surface of the sponge, it exhibits a comparatively uni- 

 form meshwork, the meshes mostly 1-2 mm. wide. 



There is no proper dermal skeletal reticulum, but just below the 

 dermal surface the most peripheral of the connectives form a tangen- 

 tial network which may be designated a subdermal reticulum. This 

 is perforated by rounded spaces, for the radial canals, 1-2 mm. in 

 diameter. Such spaces are commonly about 2 mm. apart, the interven- 

 ing reticulum showing meshes which grade down from 1 mm. to 

 about 150 \i in diameter. 



Holotype.—G%t. No. 21299, U.S.N.M. 



F. E. Schulze in his classical essay on Spongelia (18796) recog- 

 nizes (p. 127) the impossibility of separating the group of Adriatic 

 forms into sharply distinct species. Intermediates occur between 

 ail subdivisions, and holding this in mind all the Adriatic Spongelias 

 (avara, p(dle8C&n#, elegans, spinifera) might be regarded as varieties 

 of one species. 



Under the name of S. pallescens O. Schmidt, Schultze (18796, 

 p. 138) combined with that sponge several others of Schmidt's 

 (18G2, 1864) Spongelias. In the species so conceived Schulze finds 

 (p. 141) the form, consistency^, and color variable. The conuli are 

 fairly uniform, 1-3 mm. high and 1-3 mm. apart. Radial main fibers 

 and connectives are readily distinguishable. The main fibers, 1.5-2 

 mm. apart in the body of the sponge, terminate in the conuli, and 

 are thickly filled with foreign particles, chiefly sand grains. No 

 mention is made of any tendency in the main fibers to become fas- 

 cicled. The connectives are cylindrical and considerably thinner 

 than the main fibers, sometimes completely filled with foreign par- 

 ticles, sometimes practically without such, the two extremes con- 



