508 ARACHNIDIID.E. 



which is furnished with eighteen arras, and is by no 

 means a pygmy. The tentacular wreath presents a most 

 elegant campanulate figure, with an everted margin. 



In the young cells the form is hexagonal and very regu- 

 lar, the outlines are distinctly defined, and the walls are 

 almost hyaline. At this stage few spines are developed ; 

 only an occasional one is to be met with. In many cases 

 these appendages are confined to the neighbourhood of 

 the orifice, around which as many as five to seven are often 

 ranged ; but in others they surround the cell, and are 

 placed along the margin in a row, bending inward over 

 the front surface. Apart from this important variation, 

 they differ considerably in number. Each spine rises 

 from a swollen base. 



In the older parts of the colony the cells are crowded 

 together, and lose their regularity of form. 



Family III. Arachmdiidae. 

 ALCYONIDIADJJ (part.), Hincks (1862) : Alder. 

 ZOCECIA usually more or less distant, membranous. 



Genus ARACHNIDIUM, Hincks. 



Der. Dim. of upa^viov, a spider's web. 



AIIACHNIDIA, Hincks, Cat. Devon and Cornw. Zooph: Alder. 

 AKACHKIDIUM, Hincks, Ann. N. H. for Sept. 1877. 



GENERIC CHARACTER. ZOARIUM membranaceous. Zo- 

 CECIA usually separate, distant, adnate, united by a more or 

 less filiform prolongation of the cell-wall, so as to form a 

 delicate network. 



