ECHINODERMATA OF NEW ENGLAND. 53 



Aslrangia. Skeleton calcareous encrustations. Not 

 branching. Individuals closely crowded. Corallum cir- 

 cular, sometimes polygonal by crowding. Septa of equal 

 size, not prominent, peripheral wall. Polyps cylindrical, 

 tentacles numerous, dotted with clusters of nematocysts. 

 Terminal clubs. Tentacles retractile. Ova vomited 

 through month when laid. South of Cape Cod. 



A. Dance. 



A. III. 



llyanthus. Body free, tapering posteriorly. Tenta- 

 cles slightly retractile. No posterior orifice. 



/. lasvis. 



Cereanthus. Body elongated, vermiform. Two series 

 of tentacles which alternate with each other. Posterior 

 part present. 



C. borealis. 



Edwardsia. Colonial, not attached by coenosarc. Pos- 

 terior extremity inflated, not perforate, membranous. Ten- 

 tacles on a retractile column. Motion in retraction rapid. 

 Color white. Young, Arachnactis.* 



E. sipunculoides. 



farinacea. 



sulcata. 



carnea. 



lineata. 



Philomedufta. Body vermiform with posterior sac. 

 Posterior opening? Tentacles few, short, thick, conical. 



P. parasitica. 



Madreporaria. 



Solitary or colonial. Secrete lime skeletons. Tenta- 

 cles numerous, hollow ; no external opening, retractile. 



1 The young of E. lineata 1 is said to be the Actinian parasite of Mnemiopsis. 



