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. 
