406 E. STECHOW. 



a gradual transition at this place. Below the hydranth there is a 

 deep constriction; the hydrocaulus which follows this begins with a 

 slight thickening, which causes the constriction above it to appear 

 still more obvious. I find it difficult, therefore, to understand how this 

 characteristic constriction could have escaped the older authors. This 

 is the chief point of difference which I find as compared with Hincks's 

 figure, but it does not seem to me sufficient to found a new species. 



The periderm is membranous, and encloses the hydrocaulus to the 

 top ; in this upper part however it is not closely attached, but lies 

 loosely around it. In the interior of the hydrocaulus below the sur- 

 face a longitudinal striation can be clearly recognised, due to the 

 longitudinal canals present in all the Corymorijhas. 



In spite of certain differences when compared with the accounts of 

 previous authors, I think' that this form may certainly be identified as 

 Halcitractiis nanus (Alder). Its transportation by a ship, under the 

 circumstances in which it was found, is also improbable. There 

 remains, therefore, only the supposition that its normal distribution 

 really extends as far south as Plymouth, and that it is only on account 

 of its rarity that it has not been previously found. 



