78 BRITISH SPONGIADJE. 



very little more than half their size. The colours and 

 mode of growth of the two sponges also differ to a 

 very considerable extent. 



" There are similar differences existing between the 

 sponge in course of description and H. tegeticula, in 

 which the skeleton spicula are much shorter than those 

 of H. solidus, and exhibit none of the marked inequali- 

 ties of size and diameter that are so characteristic of 

 that species, but, on the contrary, are very equable in 

 size and proportions. In the dermal membrane the two 

 species differ also to a very considerable extent. In 

 H. tegeticula the dermal spicula are more or less felted 

 together, instead of presenting a well-defined but irre- 

 gular reticulation. The colour and mode of growth 

 are also strikingly different from those of H. solidus. 

 If any doubts remain regarding the discrimination of 

 the three species, the comparative measurements of 

 their spicula will readily determine the question. 

 Thus the large spicula of H. solidus measure -^ inch 

 in length, and have their greatest diameter 20 1 00 inch. 

 H. reticulatus has its largest spicula -j^ inch in length, 

 and the greatest diameter 3^0 inch. H. tegeticula has 

 its largest spicula -^ inch in length, and their greatest 

 diameter -g-^or inch. 



" I have since the above description was written re- 

 ceived another specimen of this from Mr. Norman, 

 which differs in its external characters from the type. 

 It is a small, irregularly shaped mass an inch and 

 a half in length, embracing a small fragment of 

 stone, from which it does not project itself as the type- 

 specimen does. It also differs in colour, being nearly 

 cream-white. Anatomically it agrees perfectly with 

 the type-specimen." 



