GEODIA ACANTHTi^ASTRA. 



191 



The clades are conic, pointed or blunt, and slightly curved, concave to the 

 epirhabd. They are fairly equal (Plate 45, figs. 1, 3) or considerably unequal 

 (Plate 45, figs. 2, 6) in length. The longest clade of the cladome is 55-130 p. long. 

 The chords of the clades enclose angles of 31-53°, on an average 39°, with the 

 axis of the epirhabd. The epirhabd is straight, conic, and 30-85 n long. Its 

 length usually is from a third to a half of the length of the longest clade. 



The anatriaenes (Plate 45, figs. 8-15, 19c) have a rhabdome 3-5.4 mm., mostly 

 about 4.7 mm. long and, at the cladome, 18-28 /< thick. The cladome is without 

 an apical protuberance. The clades are stout, fairly equal, conic, considerably 

 curved, concave to the rhabdome, in their proximal part, and slightly curved in 

 the same direction or straight in their distal part. Their chords are 50-110 n 

 long and enclose angles of 38-56°, on an average 45.3°, with the axis of the rhabd- 

 ome. In the small, probably young, anatriaenes, in which the rhabdome is, 

 at the cladome, only 5 13 /_< thick and the clades only 30-46 long, the clade- 

 angles are much larger, 52-58° wide (Plate 45, fig. 9). 



Besides the microsderes mentioned above which have been observed in situ 

 in the sections, oxyasters and a large strongylosphaeraster were found in the 

 centrifugal spicule-preparations. These, particularly the large strongylosphaer- 

 aster, may be foreign to the sponge, but since this is doubtful I think it better 

 to describe them here, together with the asters, which undoubtedly form part of 

 the skeleton proper. 



The oxTjastcrs are of two kinds, smaller and larger ones. The smaller oxy- 

 asters, which are, in the centrifugal spicule-preparations, relatively much more 

 numerous than the larger ones, are without centrum and have from five to ten 

 straight, conic rays, 12-15 // long and, at the base, 0.7-3 /i thick. The distal 

 two thirds of the rays are covered with spines. The total diameter of these asters 

 is 22-29 i-i. The larger oxyasters are similar to the small ones, have six or 

 seven rays, about 20 p. long and 3 /x thick at the base, and measure 36-38 p. in 

 total diameter. 



The large oxysphaerasters (Plate 46, figs. 10-13) are connected with the 

 small strongylosphaerasters by transitional forms. Some might also be consid- 

 ered as transitions between the oxysphaerasters and the oxyasters described 

 above. Before dealing with these transitional forms I will describe the true 

 oxysphaerasters (Plate 46, figs. 10-13). These have a spherical centrum, 3.5- 

 5 p, from a quarter to a third of the whole aster, in diameter. From this from 

 twelve to twenty-six, rather regularly distributed concentric rays arise radially. 

 The rays are straight, conic, sharp jDointed, without centrum, 3.7-7 p long, and, 



