HYDROIDA. BALE. 281 



doubt. Stechow, Warren, and Vanhoffen regard them as 

 belonging to one species, but Billard considers S. mediterranea 

 as sufficiently distinguished by the presence of internal teeth 

 in the hydrotheca. This, however, is not in accordance with 

 the definitions of Hartlaub, who says that S. polyzonias also 

 possesses these appendages, though they are not so strongly 

 developed as in S. mediterranea, and may be entirely wanting. 

 He mentions further that he has seen specimens which he 

 is in doubt whether to place under S. mediterranea or S. 

 polyzonias. All this may be regarded as favouring the view 

 of those observers who consider the two species identical ; 

 but on the other hand it seems equally reasonable to suppose 

 that Hartlaub was wrong in assigning to S. polyzonias any of 

 the specimens with internal teeth, and that Billard's view 

 is the correct one. Stechow's reason for believing the species 

 the same was that he had found specimens with internal 

 teeth therefore to be referred to S. mediterranea but with 

 an external marsupium on the gonotheca, the latter con- 

 dition being characteristic of S. polyzonias. This, however, 

 is quite in accordance with Hartlaub's statement that 8. 

 polyzonias may have internal teeth, which both Stechow and 

 Billard omit to notice. 



The position then seems to be that Hartlaub makes the 

 presence or absence of the marsupium the prime specific 

 character, while Billard regards the internal teeth as of more 

 importance. 



Dr. Ritchie, who has kindly sent me British specimens of 

 8. polyzonias, informs me that he has examined colonies of 

 that species from a number of widely separated localities, 

 and has in no case found internal teeth present. 



All the Australian specimens which I have so far observed 

 possess these teeth, and therefore conform to Billard's 

 description of S. gaudichaudi (S. mediterranea) ; I therefore 

 refer them to that species, leaving for future settlement the 

 question of its identity or otherwise with S. polyzonias. 



I only saw one fragment among the " Endeavour " material, 

 and am doubtful as to its locality ; it agreed, however, with 

 Port Phillip specimens which I formerly described as S. 

 polyzonias. The shoots are simple or with few and irregular 

 branches, given off below the hydrothecae, just as in S. 

 polyzonias 1 ; the hydrothecse are adnate for about half their 

 length. In certain minor particulars they differ from 

 Billard's description ; thus the hydrothecae are in one plane 



1. In the specimen of S. polyzonias sent to me from Scotland by Dr. 

 Ritchie, about half the branches spring from the interior of hydrothecae. 



