ADDITIONS. 



In tlie gradual accumulation of tlie material for the 

 history of the British Spongiadaa many of the species 

 have been described and figured from single specimens 

 in an imperfect state of preservation and from small 

 portions or even fragments only, of the perfect sponges. 

 Since the publication of the descriptions in Vol. II, 

 and also since the delineation of the figures in Yol. Ill, 

 I have been in the habit of receiving from various 

 sources fresh specimens of rare and unique species in a 

 fine state of preservation, frequently affording addi- 

 tional information regarding their structure and habits, 

 or strong confirmatory evidence elucidating doubtful 

 points in their history. I have, therefore, thought it 

 advisable in all such cases to publish the results of the 

 examination of such specimens, as a supplement to the 

 histories of the respective species to which they are 

 related, and for the greater facility of reference. I 

 have arranged these notes under the heads of their 

 respective genera, rather than in the order in which 

 they have been acquired. 



The following is a list of the genera and species 

 thus treated on. 



Ecionemia ponderosa. 

 Microciona fiditia. 

 Hymeniaciclon coccinea. 

 — placentula. 



