28 Rev. T. Hincks on the 



the centre of the lower margin, the rest of the peristome occu- 

 pied by 6-10 tubular spinous processes, a denticle within the 

 peristome on the lower primary margin. Avicularia none. 

 Ooecium (fig. ^h) rounded, developed behind the neck-like peri- 

 stome (the orifice, with its full armature of spines, rising before 

 it), sometimes traversed by a number of the immersed tubules. 

 Primary cell (fig. 3 a) small, ovate ; aperture occupying about 

 two thirds of the front surface, surrounded by a raised border, 

 which bears about 8-10 spines ; the orifice nearly semicircular, 

 occupying the upper portion of the aperture, the lower part 

 closed in by a delicate membrano-calcareous covering ; por- 

 tion of the cell below the aperture smooth and solid. 



Zoarium forming very large cream-coloured crusts on shells. 



Extremely abundant; probably the commonest species 

 amongst Dr. Dawson's dredgings. 



[Bass's Straits {CajJt. Cawne Warren).] 



I have ranked this interesting form as a variety of 31. 

 spinosissimay a species which I have described and figured in 

 my report on the Polyzoa of Bass's Straits (' Annals ' for Aug. 

 1881). In all the principal elements of structure there is an 

 exact correspondence between the two; but there are also one or 

 two differences, which materially affect the general appearance, 

 and, at the first glance, few probably would be likely to iden- 

 tify them. In the present variety the cells are very much 

 larger than those of the Australian form. The latter are small 

 and delicate, while those of the variety major are ample, 

 broadly ovate, massive, and strongly built. But the chief 

 difference between them lies in the system of tubules, more 

 or less immersed in the cell-wall and showing as white strise 

 on the glossy surface, which gives so distinctive a character 

 to the North-Pacific form. Of this tubular structure I have 

 been unable to detect any trace in the Australian specimens 

 which I have examined. Possibly the condition of the stony 

 crust may be such as to conceal it ; but this hardly seems 

 probable, as in the finest colony which has come under my 

 notice calcification has evidently not proceeded far. It may 

 also be noted that the cells of the Australian variety have 

 well-marked row of punctures round the margin. 



At present, looking to the close structural agreement be- 

 tween the two forms, and in the absence of any precise know- 

 ledge as to the development and function of the tubules, I 

 prefer to include them in one specific group. 



The tubules appear as delicate white lines through the 



• subhyaline crust, radiating from the circumference towards 



the centre of the zooecium. They vary much in length, some 



being almost rudimentary, and others extending nearly or 



