SPONGES OF THE ORDER ECHINONEMA.TA. 497 



DESCRIPTION OF THE PLATES. 



Plate XXYIII. 

 Figs. 1-6. Echinodictyum bilamellatum. 1. Portion of surface of inner aspect 

 of sponge, from type in Paris Museum, x 38 cliam. 2. External 

 part of section perpendicular to inner (upper) surface of cup, X 38 

 diam. (from the British-Museum specimen from N.W. Australia). 

 3 & 4. Skeleton acerate spicules, X 68 diam., from type specimen. 

 5. Spined cylindrical echinating spicule, X 370 diam., from type speci- 

 men. 6. The British-Museum sponge (E. bilamellatum) from N.W. 

 Australia, reduced to one third nat. size. 

 7-10. Echinodictyum nervosum. 7. Part of surface, X 50 diam. 8. Part 

 of section perpendicular to branch, X 50 diam. 9. Skeleton acerate 

 spicule, X 68 diam. 10. Spined cylindrical spicule, X 370 diam. 



Plate XXIX. 

 Figs. 1 & 2. Dirrhopalum gymnazon. 1. Tricurvate flesh-spicule, X 370 

 diam. 2. Equianchorate flesh-spicule, X 370 diam. 



3-7. Dirrhopalum coriaceum. 3. Equianchorate flesh-spicule, X 370 

 diam. 4. Dumbbell spicule, X 370 diam. 5. Tricurvate flesh-spicule, 

 X 185 diam. 6. Smaller (spined) acuate spicule, X 185 diam. 

 7. Head of larger (smooth) acuate, X 370 diam. 



8-17. Dirrhopalum novizelanicum. 8. Large skeleton acuate (no. 1), 

 X 68 diam. ? 9. Smaller skeleton acuate (no. 2), X 68 diam. 10. 

 The same, head, X 370 diam. 11 & 12. Fine spinulates of flesh 

 (no. 4), X 68 diam. 13. Equianchorate flesh-spicule, X 370 diam. 

 14. Tricurvate flesh-spicule, X 370 diam. 15. Dumbbell spicule, 

 X 370 diam. 16. Portion of surface, X 30 diam. 17. Section across 

 long axis of sponge, X 30 diam. 



18-30 a. Dirrhopalum Carteri. 18. The sponge, around portion of an 

 Echin us- spine, nat. size. 19. Curved cylindrical, globose-headed, 

 entirely-spined axial spicule, magnified. 20. Cylindrical straight 

 spinulate, magnified. 21. Cylindrical curved spinulate, magnified. 

 22 & 23. Small cylindrical curved spicules, magnified. 24. Ovi- 

 spinulate subfusiform whorl-spicule, magnified. 25-27. Different forms 

 of head of 24, more highly magnified. 28. Base of the large acu ate, 

 magnified. 29. Three minute cylindrical derm-spicules, magnified. 30. 

 Diagram of the position of the spicules 19, 24, 28. 30 a. A whorl of 

 spicules round a large acuate one, which is seen in section, magnified. 



31-39. Dirrhopalum hystrix, magnified. 31. Diagram of the position of 

 the spicules. 32 & 33. Base of long acuate, magnified, showing a plain 

 ending and terminal spinulation respectively. 34. Curved dirrho- 

 palate spicule, magnified. 35. Curved cylindrical spicule, magnified. 

 36. Spicule with an irregular bend, and only one globose end, mag- 

 nified. 37. Curved cylindrical bent spicule with large spinule on it, 

 magnified. 38. Spicule with an irregular bend and only one globose 

 end, magnified. 39. Enormispinulate, magnified. 



LINN. JOURN. ZOOLOGY, VOL. XV. 39 



