510 ARACHNIDIID.^. 



marked by a small papillary rising ; but there is no promi- 

 nent tube, as in A. fibrosum. 



In the original description of this form the cells are 

 said to be furnished with marginal processes ; and Mr. 

 Alder, in his account of it, states that they occur occa- 

 sionally. On reexamination, however, I cannot satisfy 

 myself of their existence. 



Habitat. On shells. 



Localities. On a Cyprinn, dredged off the Isle of 

 Man ; on shell, Torbay (T. H) . 



Arachnidium clavatum, Hincks. 

 Plate LXXI. figs. 8-5. 



Ai!.4ciiNiDiUM CLAVATUM, Hiiicks, Auii. N. H. for September 1877. ser. 4, 



XX. 216. 

 Arachnidia iiippotiiooides, Norman, Shetland PuL, Eep. Brit. Assoc, for 



1867,311. 



Zoarium forming an irregular network. Zocecia clavate, 

 elongate, eidarged and rounded at the top, and tapering 

 otf below; orifice small, placed near the upper extre- 

 mity. 



Distinguished from A. hippothooides by its larger size and 

 its elongated, tapering, club-shaped cells. They are fre- 

 quently connected directly by the peduncular lower extre- 

 mity ; in other cases this is prolonged into a fibre. Oc- 

 casionally two or three zocecia are laid side by side and 

 apparently united. The lateral branches are given off 

 from the upper part of the cell, a little below the orifice. 



Habitat. On the tests of Ascidians, in deep water. 



Localities. Shetland (J. G. Jeffreys) : ibid. 5-8 miles 

 off Balta, on the test of Ascidia sordida (A. M. N.). 



