SPONGES OF THE OEDER ECHINONEMA.TA. 497 



DESCEIPTION OF THE PLATES. 



Plate XXVIII. 

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

 of sponge, from type in Paris Museum, X 38 diam. 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 ecliinating 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. Birrhopalum gymnazon. 1. Tricurvate fiesh-spicule, X 370 

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



3-7. Birrhopalum coriaceum. 3. Equianchorate fiesh-spicule, X 370 

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

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

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



8-17. Birrhopalum 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 fiesh-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. Birrhopalum Carteri. 18. The sponge, around portion of an 

 Echinus- 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 acuate, 

 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. Birrhopalum 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. JOUEN. — ZOOLOGY, VOL. XV. 39 



