434 PROCEEDINGS OF THE ACADEMY OF [1898. 



which run in bundles through the sponge walls, x 56. 1 a^ 

 middle region of the same showing a slight enlargement,, 

 and the axial fibre with the two reduced transverse axes. 

 x250. 



Fig. 2. A short, thick diact, with transverse limbs entirely sup- 

 pressed, with slightly enlarged rounded ends, and axial 

 fibre almost gone, x 56. 



Fig. 3. A small, slender and straight diact, with transverse limbs 

 indicated as rounded nodules, with ends pointed and 

 roughened, and axial fibres complete, x 56. 3 a, one of the 

 ends of the same, x 250. 



Fig. 4. A small, slender, curved oxy-diact, with transverse limbs 

 distinctly indicated as four nodules, x 56. 3 a, middle 

 region of the same, x 250. 3 b, one of the ends of the 

 same, x 250. 



Fig. 5. A peculiarly modified end of a large diact, showing a zig- 

 zag course of the axial fibre, x 56. 



Fig. 6. A portion of the sponge base showing the secondary union 

 of spicules by the formation of encrusting and cementing 

 deposits and numerous synaptacula. At a, the encrusting 

 layers are represented as broken away, exhibiting the 

 original diact. x 56. 



Fig. 7. A group from one of the bundles of minute acicular diacts 

 found in the superficial parenchyma about the handles of 

 the sword-shaped hexacts. x 56. 



Fig. 8. An oxy-hexaster in which the axial rays are continued be- 

 yond the place of branching, x 500 



Fig. 9. One of the usual type of sword-shaped hexact. x 56. 9 a, 

 b, c, are respectively enlarged views of the handle, tip of 

 one of the cross pieces and the point, x 250. 



Figs. 10, 11 and 12. Three of the sword-shaped spicules, x 56. 10 

 is short and regular; 11 has the blade bent and the cross 

 rays rough, uneven and thickened ; 12 is straight, with 

 the cross pieces bent sharply upward toward the handle. 



Fig. 13. A small, spiny, regular oxy-hexact. x 56. 13 a, one of the 

 rays enlarged, x 250. 



Fig. 14. A rosette in which the axial rays are continued beyond the 

 disk, and the number of terminal rays is small and con- 

 fined to the margin of the disk, x 250. 



Fig. 15. A rosette with roughened axial or stem rays terminated 

 by disks bearing a close brush of fine terminal rays, x 340. 



Fig. 16. One of the simpler disco-hexasters with distinct stem rays, 

 and sixteen terminal rays in each group. The disks or 

 pin-heads have usually sixteen marginal teeth each. x250. 



