in the exterior Rays of Actinia. 253 



very long and delicate fibre (See fig. 1, a.) These spiculse 

 resembled so much, in their form, perforation, and general ap- 

 pearance, some of the fossil siliceous spiculse above referred 

 to, that, like the fossil ones, they must be siliceous. This 

 question I had not the means of deciding, but I hope it will 

 be settled by some of the Boston naturalists. It is only ne- 

 cessary to burn one of the rays and examine the ashes ; the 

 siliceous spiculstj will of course, retain their form after igni- 

 tion. It would be an interesting fact, if, by means of these 

 spiculas, we could obtain evidence of the existence of species 

 of Actinia during the epoch of the Eocene tertiary ; for who 

 would expect that such soft and perishable creatures could 

 leave, for such a length of time, any trace of their existence. 



The annexed sketches (See fig. 1, a. b, c,) were made mere- 

 ly as memoranda as I hoped to have further opportunities 

 for observation. They will serve to indicate the form and 

 position of the spicules although they have no pretensions to 

 accuracy. 



The siliceous Bacillaria, of Boston Harbor, appear to be 

 numerous and elegant. 



The following is a list of the chief species noticed by me 



in April, 1842. 



Ceratoneis fasciola, ) motions very active. These spe- 

 Ceratoneis closteriujn, ^ cies were recently discovered by 



Ehrenberg. Figures may be found in a late number of the 



Berlin Transactions. 



Coscinodisciis radiatus, fragments only were observed. 



Coscinodiscus ,or Actinocycliis 7 Toriform-siliceous bodies 

 were observed in the living state containing a yellowish brown 

 matter disposed in 5 or 6 radiant portions, each of which was 

 repeatedly branched. 



Gallionella sulcata. 



Gallionella 7nonilifor7nis. 



Navicula viridis, living in salt water, but diilering in no 

 respect from the fluviatile species. 



Navicula , Plate II. fig. 18, of Bailey's sketch of 



American Bacillaria. 



Fragillaria , a marine species with very llexible 



