THE EXCAVATING SPONGES. 



353 



occasionally a little bent, and strongly spined ; with the extre- 

 mities obtuse. 



Only one specimen of this species has been obtained ; it occurs 

 in the shell of a Serpula adhering to a Chama, from Mazatlan, 

 presented to the Newcastle Museum by Dr. P. P. Carpenter. 



EXPLANATION OP PLATES. 



PLATE XVI. 



Fig. 1. Spicula of Cliona Northumbrica : a, pin-like spicula ; b, fusiform 

 ditto ; c, the minute or third form of ditto. 

 The minute or third form of spicula of C. vastifica. 

 The minute or third form of spicula of C. corallinoides. 

 Ditto ditto of C. gracilis. 



Ditto ditto of C. Howsei. 



Ditto or second form of spicula of C. lobata. 

 Spicula of C. celata. 



A few of the cells of Orbitoides Fosteri from Dr. Carpenter's 

 figure after Ehrenberg ; a, cell, next primordial cell ; b, b, 

 stolons or stems uniting the cells. 

 Fig. 9. A portion of an undescribed Cliona immersed in the shell of Pecien 

 magettanicus : a, a, lobes of the sponge corresponding to the 

 cells in fig. 8 ; b, b, stolons or stems. 



Fig. 



o 



Fig. 



3. 



Fig. 



i. 



Fig. 



5. 



Fig. 



6. 



Fig. 



7. 



Fig. 



8. 



Fig. 



1 



Fig. 



2 



Fig. 



3 



Fig. 



4 



PLATE XVII. 



Spicula of C. mazatlanensis : a, pin -like spicula; b, fusiform ditto ; 



c, c, minute or third form of ditto. 

 Spicida of C. vermifera : a, pin-like specula ; b, b, the second or 



worm -like ditto. 

 Ditto of C globulifera. 

 Ditto of C. Carpenteri: a, a, pin-like spicula; b, fusiform ditto; 



c, c, the third or minute form of ditto. 



