24 



THE SPONGES. 



conspicuously curved as in Plate 2, Fig. 9. When the rays are curved, 

 the curvature is of the usual character, viz. opposite rays of a diameter are 



bent in opposite directions. 



The dermal and gastral pinuli are alike, and are pentacts. The distal 

 ray (Plate 2, Figs. 2, 3) is comparatively stout, ending above in a ter- 

 minal cone. In the upper half of the ray the spines are long, narrow, 

 and appressed. Below they are shorter and project outward in hook-like 

 shape, degenerating farther down into a few prickles. The lowest part 

 of the ray is smooth. The tangential rays bear a few scattered, sharp 

 microtubercles. The range of size is considerable. Large spicules are 

 abundant (Fig. 2, Plate 2) in which the distal ray is 530 /x long, with a 

 greatest thickness of 64 /x and a basal thickness of 24 /x ; tangential rays, 

 44 /x x 16 /x ; spines on distal ray reaching a length of 40 /x, measured 

 along their upper border. Smaller spicules (Fig. 3, Plate 2) are abundant 

 down to a size in which the distal ray is 250 /x long, with greatest thick- 

 ness of 32 /x, and a basal thickness of 10 /x; tangential rays, 30 /x x 10 //,. 

 Still smaller sizes (Fig. 4, Plate 2) occur, although not commonly, in which 

 the distal ray may be only 175 /x long. Some of the shortest spicules 

 have tangential rays as long as are met with in any of the pinuli, the 

 length reaching 60 /*,. Although the size of the pinuli varies within such 

 wide limits, the character remains fairly constant. The character is 

 expressed especially in the terminal cone, the long and narrow appressed 

 upper spines, and the lower hook-like spines. 



The macramphidiscs are of two types. The first type of macramphidisc, 

 Fig. 8, Plate 2, is only moderately abundant. It occurs, in the present 

 condition of the specimen, both at the surface and in the interior. The 

 shaft is slightly expanded, not always symmetrically, at the middle, 

 and is smooth or bears one or two scattered small, sharp protuberances. 

 The umbel is rather evenly rounded, although somewhat truncated at the 

 apex, where there is a depression. It is considerably wider than deep, and 

 its depth is from \ to f the total length of the spicule. There are 8 rays 

 which are acutely pointed. The variation in size is not great, and a typical 

 spicule has the following measurements: total length, 455 /x ; depth of 

 umbel, 122 /x; greatest width of umbel, 188 /x ; greatest width of umbel 



- 



ray, 36 /x; thickness of shaft, at the middle of spicule, 30 /x. 



The second type of macramphidisc is more abundant. It occurs espe- 

 cially at the surface, or in the peripheral parenchyma. In this spicule 











