THE EXCAVATING SPONGES. 347 



spicula in the former are put in italics, so that the reader may 

 see at a glance what is now added. 



Cliona celata. PL XVI, fig. 7. 



Spicula pin-like, long, and stout, a little fusiform, and some- 

 what bent, measuring upwards of -g^-th of an inch in length ; the 

 head is well defined, globular, approaching to ovate, with gene- 

 rally a terminal obtuse point, being placed not exactly at the 

 end of the shaft. 



C. gorgonoides. 



Spicula pin-like, large, and stout, measuring -§Vth of an inch 

 long ; the head oval, and frequently at some little distance from 

 the extremity; from thence the shaft gradually tapers to the 

 other or pointed end, and is usually much bent, particularly 

 towards the head, and sometimes the pointed extremity is a little 

 recurved. 



This is a critical species, and is probably a mere variety of C. 

 celata. 



C. NoRTOTJMBRICA. PL XVI, fig. 1. 



Spicula of three kinds : the first much the largest, measuring 

 - 7 Vth of an inch in length, is pin-like, straight, sharp pointed, 

 with the head large, round, and terminal : the second kind is 

 fusiform, scarcely more than one-fourth the length of the first, 

 rather stout, much and suddenly bent in the centre, with both 

 ends sharply pointed, and when viewed through the ith of an 

 inch object glass is seen to be minutely spinous : the third form 

 very minute, leing not more than the Titooth of an inch long ; it is 

 cylindrical, lent sharply in the centre, and apparently smooth under 

 the %th of an inch object glass, though occasionally there are slight 

 indications of spines ; the extremities are recurved, slightly enlarged, 

 and rounded. 



The second and third forms are more numerous than the first, 

 which is most abundant in the papillae. 



When dry the sponge is of a pale, clear ochreous-yellow colour. 



