198 FLORENCE BgCHANAN. 



forms, and did not concern myself with hunting for the fuller 

 description before sending my paper to the press. 



From the description which I have now seen, it appears to 

 me highly probable that Hekaterobranchus will have to be 

 regarded, for the present at least, in virtue of its single pair of 

 branchiae placed on the head, its ventral collar, and its dorsal 

 collar (equivalent to the so-called dorsal ''pouch " of Webster), 

 as a new species of the genus Streblospio, rather than as a 

 distinct genus. There are, however, differences between the two 

 forms, which might rank as generic differences were there a large 

 number of forms with their common characteristics known. 

 For instance, the " conical median papilla or cirrus " on the 

 anterior margin of the first segment, the short conical dorsal 

 cirri of the posterior segments succeeding and replacing the 

 plate-like lobes of the anterior, the fact that the " pro- 

 boscis is incomplete above " (though, as I have failed to grasp 

 what this means, I cannot attach much importance to it), the 

 absence of thoracic nephridia (unless the dark green colour 

 observed in the first eight segments of a few specimens was due 

 to their presence), are all features in Streblospio which might 

 prevent the association of Hekaterobranchus with it as one 

 genus. How much, or how little, importance is to be attached 

 to these differences is difficult to say without comparing the two 

 forms, or at least proper representations of them, side by side. 

 The drawings published by Mr. Webster of his Streblospio are 

 so fragmentary and rough that I cannot undertake to form a 

 final opinion on the subject by their aid alone. 



