316 PEOF. p. M. DUNCAN ON THE 



VI. JEtemarhs on the Anatomy of Siderastrsea, Meruliua, and 

 Echinopora. 



Grenus Sideeaste^a, Blainville. — Syn. Astrsea, Oken. 



Tl]is genus, partly established by Lamarck and Blainville, is 

 the Siderina of Dana, and was termed, after a careful study, 

 8iderastrcea\)j Milne-Edwards and Jules Haime. In their great 

 work these last-named zoophytologists altered the uame to Astrcea, 

 given by Oken in 1815. 



In the diagnosis of the genus Milne-Edwards and Jules Haime 

 state, with regard to the septa, " The sides are covered with very 

 large granules which often meet (across the interseptal loculi) 

 those of the opposed septa, and unite so as to form incomplete 

 synapticula. The endotheca is rudimentary." 



Pourtales has drawn, in his ' Florida Corals,' a beautiful sec- 

 tion of a Siderastrcea, and shows that the calices have walls, and 

 that there are rows of synapticula besides granules, and some 

 endothecal dissepimental tissue. 



In the species I have examined from the American and Indian 

 seas the drawing of Pourtales is substantiated. The synapticula 

 are not enlarged granules, and are in regular vertical series with 

 but little space between them w'hen they are placed one above 

 the other on the septa. There are granules in abundance around 

 them and nearer the internal edge of the septa also. 



Endothecal dissepiments also exist crossing the line of the 

 synapticula ; and they are normal structures, not being developed 

 in consequence of annelid growths, as in Mceandroseris and other 

 forms. The true wall separates the calices, and the interseptal 

 loculi are intruded upon by the rows of synapticula near the wall 

 and by the dissepiments. 



Dana evidently considered this genus to belong to the Fungidse ; 

 for he terms one species Pavonia { = Loplioseris) Siderea. 



It is evident that the presence of endothecal dissepiments is a 

 marked feature in this genus ; moreover, the living part, when 

 expanded, resembles that of the Astrseidse. It cannot therefore 

 enter the Fungidse proper, where my late friend Pourtales 

 proposed to place it. 



Genus Meeulina, MihieSdwards ^ Jules Haime. 

 This genus is placed in a transition group between the As- 

 trseidse and the Eungidse. 



