138 PLATE LIV. 



based on a black pebble, from Shetland, preserved in 

 salt and water as it came from the sea. Natural size. 



The oscula are rarely to be seen in specimens in the 

 wet condition. 



Fig. 7. Two of the attenuato-acuate spicula, of the 

 primary lines of the skeleton. X 80 linear. 



Fig. 8. -Two of the acerate spicula, of the secondary 

 lines of the skeleton. X 80 linear. 



The two sizes of spicula represented by figs. 7 and 8 

 are about the largest and smallest of each form. The 

 intermediate sizes are the most numerous. 



Fig. 1, Plate XIV, in the present volume, exhibits a 

 specimen of I. infuiidibuliformis containing a fine 

 specimen of Tethea cranium. The sponges are in the 

 condition in which they came from the sea, having been 

 preserved in a saturated solution of salt in water. In 

 this specimen the oscula are not so distinctly visible as 

 in the dried one. 



