BY W. A. HASWELL, M.A., B.SC. 43 



penetrates about lialf the thickness of the zoarium, gradually 

 narrowing as it descends. 



58. Myriozoum australiense, sp. nov., Plate III., figs. 9 — 11. 



The extra-opercular portion of the cell in this species is very 

 prominent, and displays a little below the mouth a rounded 

 aperture. The margin of the mouth is crenulated, and there is a 

 rather prominent, bifid lower lip. The operculum is situated 

 deeper than the level of the general external surface of the 

 polyzoary. The cells are separated from one another by delicate 

 radiating partitions, and the breadth of each is circumscribed in 

 the older and thicker branches of the polyzoary by delicate semi- 

 transparent lamellae, which extend from the outer wall, just below 

 the operculum of the cell downwards and inwards so as to cut off 

 an internal and an external chamber, the former dilating upwards 

 and occupied by the polypide, the latter empty. In the younger 

 portions of the polyzoary the radiating septa sometimes meet in 

 the centre ; in the older portions in which the number of cells in 

 each whorl is greater, there is a central axial canal within the 

 walls of which the septa do not extend ; towards the upi^er end 

 of each internode in the neighbourhood of the thick nodal 

 transverse septum, this central canal becomes divided into a series 

 of minute canaliculi. The number of cells in each whorl varies 

 from six to ten. 



Sub-order Ctenostomata. 



59. Amathia convoluta, Lamx. 

 Hob. Port Denison and Holborn Island. 



Explanation of Plates. 



Plate I. 



Fig. 1. — Crisia terrcB-regwcB, magnified 20 diameters. 

 ,, 2. — Pusttdipora fragils, magnified 20 diameters. 

 ,, 3. — Oncliopora ventricosa, magnified 44 diameters. 



