Kirkpatrick — Hydroida and Polyzoa, Torres Straits. 621 



Operculum *14 mm. in width by - 1 mm. in length, with an 

 articular process at each proximal angle. 



Habitat. — Encrusting rock: Murray Island, 15-20 fms. 



The chief specific characters of this form are the smooth sur- 

 faces of the zooecia (surrounded by areolse) and of the ooecia, the 

 presence of a well-marked pectinate ridge, and the position of the 

 avicularium in the centre of the front wall of each zooecium. 



Cellepora discoidea, Busk, var. frittetosa, nov. var. 

 (PL xvii., fig. 3.) 



Zoarium forming a bushy growth, composed of short, stout, 

 solid, cylindrical, anastomosing branches. 



Zooecia hyaline ; orifice sub-orbicular, with three or four 

 slender denticles on the proximal border ; the rostrum short, with 

 a small avicularium with a small semicii'cular or oval mandible, 

 which latter grows longer on older cells. 



Ooecia smooth, hyaline, cucullate ; operculum semicircular, 

 with straight lower border ; "16 x - 1 mm. 



Habitat. — Albany Passage, 10 fms. ; Saibai Channel, 10-17 

 fms. ; Thursday Island (Haswell) . 



The larger of the two specimens sent is from Albany Passage, 

 and measures about 2 inches in height by 3 inches in breadth. 



The surface of the branches is covered with numerous small 

 round holes about 1*05 mm. in diameter ; these are the orifices of 

 a parasitic or commensal " Actiuid," first observed by Mr. 

 Haswell, 1 who saw the mesenteries. The tubes do not penetrate 

 far, and have csecal endings ; often two or three communicate, 

 and have a common csecal termination. 



Cellepora discoidea, var. frutetosa, may possibly be simply the 

 adult form of Cellepora discoidea, Busk. There is a resem- 

 blance in the general form and appearance of the cells, in the 

 shape of the orifice, presence of denticles, and in the size and 

 shape of the operculum. The variation from the type consists in 

 the smaller size of the rostra and rostral avicularia, and in the 

 mode of growth. 



1 " Proc. Linn. Soc. N. S. Wales," vol. vii., p. 608, 1882. 



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