PLATE LXXII. 195 



There are but two among the known species of 

 British Polymastia with which the species under con- 

 sideration is liable to be confounded by a hasty observer, 

 and these are P. robusta and P. mammillaris. The 

 short conical fistulaa and the abundant hispidation of 

 its basal surface, contrasted with the smooth basal 

 mass and the elongate fistulse of the first-named spe- 

 cies of the two will readily distinguish them, indepen- 

 dant of the more decisive character arising from the 

 difference in form of their respective skeleton spicula. 

 It may also be readily separated from P. mammillaris 

 by the difference in the forms of their skeleton spicula 

 and the smoothness of the basal surface of the last- 

 named species. 



Since the above description was written I have re- 

 ceived two more specimens of the species from Mr. 

 Norman. One is rather less than that which is figured. 

 It has two conical fistula, but one of them is very 

 much smaller than the other, but the general resem- 

 blance is very close to that of the type-specimen. The 

 other specimen is about half the size of the figured 

 one, and it has but one conical fistula, but is a complete 

 and perfect specimen. 



