BEITISH SPONGIADjE. 73 



the same form as those of the secondary series of external 

 defensive ones, but they are' usually much larger and longer. 

 I have compared the specimens sent me by Mr. Hyndman, 

 from Larne Lough, with the type of Montagu's Spongia 

 penicillus, in the possession of Dr. Grant, and there is no 

 difference between the two, either in external appearance 

 or in structural characters. Montagu says : — " In drying, 

 the tubes become compressed and a little arcuated, and all 

 incline the same way ;" and this is precisely their condition 

 in the Larne Lough specimens, not only when dried, but 

 when preserved in spirit fresh from the sea. No reasonable 

 doubt therefore, remains, that the specimens dredged by 

 Messrs. Thompson and Hyndman in Strangford Lough, in 

 1835, and sent to Dr. Johnston, and those dredged by 

 Mr. Hyndman in Larne Lough, which were sent to me, 

 are identical with Montagu's Spongia penicillus, and are 

 therefore entitled to be considered as correct types of 

 Johnston's Halichondria mammillaris. It is necessary to 

 be thus particular in our recognition of the species, as a 

 doubt might otherwise hereafter exist as to whether the 

 sponge sent to me by Profe§sor King, and designated by 

 me Polymastia robusta, might not have been the original 

 Spongia mammillaris of Johnston. 



Montagu in describing Spongia penicillus, writes that : — 

 " The interior substance of this species is precisely that of 

 {Teihed) lyncurium, but instead of being orbicular, it 

 spreads horizontally upon marine bodies, and shoots upwards 

 from its surface cylindrical tubes, of nearly an inch in length, 

 which have an opening at the apex." Dr. Johnston, pro- 

 bably on the authority of Montagu, repeats this assertion ; 

 but in the dried type specimen from Montagu's collection, 

 there are no remains of such an open condition of the tubes 

 as that described by him in the Wernerian Memoirs, and 

 in no specimen of this or any other allied species of 

 Polymastia, have I even been able to discover any such 

 opening, or any distinct indication of such an opening, and 

 I can only account for Montagu's assertion that such open- 

 ings existed in any specimen in his possession, by the 

 supposition, that the apices of the cloacal fistulse had some 



