EXPLANATION OF THE PLATES. 
PLATE L 
Fig. 1—8. Thenea muricata (Bwk.) Gray. 
(All figures natural size; figg. 1, 2, 3, 4 and 8 after var. z, figg. 5, 6 after 
Fig. 1. 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 7. 
Fig. 8. 
Fig. 9. 
var. ß; fig. 7 after var. y.) 
Specimen with five straight roots and one tuft on the top. The broad 
split shows the membrane with the pores. 
Specimen with one great root in the middle and five smaller ones 
around it. On the top is one slender flexuous tuft. The penthouse 
with its long needles is on the left side. In this specimen the casque- 
shape is very apparently. 
Elongated form. 
Section through a specimen like n°. 2. 
Section of n°. 6. In the middle is to be seen the centrum from which 
the radii of spicules go out. Two penthouses. 
Specimen more rough than 1, 2 and 3. The two roots divide them- 
selves on the end. No tuft; two penthouse-apparatus. 
Very rugged specimen with strongly branched roots, in which many 
sand-particles are inherent. One penthouse fully developed, the 
other rather small. 
Specimen as n°. 2 seen from the top, showing one tuft and one os- 
culum with the radial canals under the dermis. 
Figg. 9 and 15. Isops pallida. n. sp. 
(natural size.) 
External of the Sponge. 
Fig. 15. Section ihrough the middle, 
