G. IDIA. 87 



a cylindrical stem ; groups distant from two to five 

 millimetres : branches diverging, coming from the stem 

 only where there are groups of cells. 

 European sea. 



IDIA. 



Pinnated, plant-like Polypidom; branches al- 

 ternate, and compressed ; cells alternate, distant, pro- 

 jecting, sharp at the summit, and curved. 



1. Idia pristis. This singular Polypidom was 

 brought by Peron and Lesueur from the coasts of 

 New Holland ; and the genus it forms is easily distin- 

 guished by the perfect resemblance of its branches to 

 the upper jaw-bone of the shark, armed with all its 

 teeth. It differs from the Sertularias by its ramifica- 

 tion, as well as by the form of its cells ; but its 

 general characters give it a decided place in our 

 second Order. 



The colour a yellow fawn, rather bright. 



Its height does not exceed a decimetre. 



Its fibrous root indicates its adherence to hard 

 bodies rather than marine plants. — Plate 5. fig. 5. a. 

 B. C. D. E. 



Australasia. 



