REPORT ON THE REEF-CORALS. 103 
varying in size from about 14 to 20 mm. in diameter and from 5 to 8 mm. in depth; 
walls simple, often quite thin, generally thickened, shghtly rounded, and about 2 mm., 
rarely 3 mm., wide. Septa unequal ; very thin within the cup, with numerous, rather long, 
fine teeth ; much thickened, and projecting but slightly at the edges, being from about 1 to 
1°5 mm. thick, with slightly swollen fistular teeth, which are often nearly 2 mm. long ; of 
five cycles in the large calicles, the last being quite incomplete and very small, distinct 
only on the sides; in the smaller calicles the fourth cycle is incomplete and small. As 
the small septa are not continued to the centre, wide and open interseptal spaces are seen, 
in the centre of which is a seant, papillose columella. 
The species seems to take an almost intermediate. position between the Acanthastreu 
hirsuta, Milne-Edwards and Haime, and the Acanthastrea angulosa, Briiggemann. 
From the former it is distinguished by the larger and shallower cells, by its thinner, 
nearly rounded, simple wall, and by the thinner, more numerous, and very unequal 
septa: from the latter, by its larger and deeper cells, by its thicker, more rounded wall, 
and by its more thickened, fistular, more equally prominent septa, which, being less 
crowded towards the centre, leave the endotheca clearly visible at the bottom of the wide, 
interseptal spaces. In the Acanthastrea angulosa, the larger septa are very irregularly 
and raggedly prominent above the thin wall, and give a striking appearance to the 
corallum. 
A single rather small specimen only was collected. 
Locality —Kandavu, Fiji. 
Genus 21. Prionastrea, Milne-Edwards and Haime. 
Prionastrea et Metastrea, Milne-Edwards and Haime, Cor., ii. pp. 513, 525. 
Prionastrexa, Duncan, Rev. Madrep., p. 123. 
This genus has been extended by Professor Duncan to include the Metastraa of 
Milne-Edwards and Haime. 
Four species were obtained. 
1. Prionastrea flexuosa (Dana). 
Astrxa flexuosa, Dana, Zoophytes, p. 227, pl. xi. fig. 6. 
The cells are very irregular, often much elongated, curved and narrow, but deep ; the 
ridges are scarcely or not at all sulcate: the septa of five cycles, the last imperfectly 
developed. The walls are often quite thin. 
Locality.—Kandavu, Fiji. 
