MADREPORARIA. 775 



2 mm. in depth. Walls up to 3 mm. thick, sharp edged against the interseptal loculi but 

 no distinct theca, slightly grooved in the centre. Septa much thicker, up to 1 mm. where 

 they pass through the theca, slightly ditFerent in size, those of the lowest (I. and II.) cycles 

 largest, 1—3 mm. (commonly about 2 mm.) e.xsert. Costae relatively thick, with low blunt 

 teeth, sometimes passing from calice to calice, but always with a distinct notch over the 

 furrows of the walls. Septa varying in number, typically 24, thinning out within the calice, 

 alternately larger and smaller, with granular sides; each provided with about six bluntly 

 pointed teeth, the third or thereabouts often longest and sometimes representing the most 

 exsert portion of the septum, no distinct paliform teeth, sometimes tertiaries fused to secondaries 

 or primaries, otherwise all merging below into the culunidla. The latter ranging in size from 

 one-third to one-half the diameter of the calice, from the surface looking fasciculated, but 

 really formed by coarse, anastomosing and uprising trabeculae from the septal edges. In 

 section the walls appearing relatively compact, partly owing to thick costae but also to the 

 relatively thick, horizontal, exothecal dissepiments, endothecal dissepiments sloping into the 

 columella at an angle of about 55 to the thecal walls, about 1 mm. apart, rather varied. 

 Increase only by intercalicinal budding. 



The form is most distinct owing to its very shallow calices, large columella and thick, 

 exsert septa. The only real variation is in the depth of the calices, those near the edges 

 being rather deeper. Of Ed. and H.'s species the specimens are closest to O. lamarckana, 

 but the costae are different. 



Locality. Minikoi, three specimens, not common, sand-flat behind boulder zone to west 

 and south of the atoll. 



37. Orbicella laxa Klz. (PL LXIII. fig. 33.) Klz., p. 49, v. 3 and x. y. 



Four specimens closely corresponding to the above description and the sections shown in 

 PI. X. fig. 9, but differing from PI. V. fig. 3, in having a considerably more solid and massive 

 appearance with calices a trifle larger (8 mm.). Budding in my specimens is intra- as well 

 as extracalicinal. 



The corallites vary considerably. In the most vigorously growing parts their thecal edges 

 may be upstanding (calices 4 mm. deep from top of theca to top of columella); septa very 

 thin, 1 — 1'5 mm. exsert, about 18 reaching the columella, most with fine paliform lobes. In 

 other parts the calice is more pad-like at the edge, no visible theca, 1 — 3 mm. deep, often 

 with additional, very small costae not represented by septa; latter thick and rough, less than 

 1 mm. exsert, 10 — 12 reaching columella with thick, blunt, paliform lobes, sometimes projecting 

 above the level of the theca. 



Locality. (1) Lagoon, flat behind Ragandi Lslet, Minikoi; (2) lagoon shoal, Minikoi; 

 (3) Hulule, west reef; (4) Goidu, sand-flat behind boulder zone. No. (3) is a separate, 

 rounded colony, 13 cm. in diameter by 8 cm. high ; the rest are larger blocks from the living 

 edges of great massive colonies, most parts of which have for some cause or other been 

 killed. Colour, light green over the theca, very dark orange-green on the peristome. 



38. Orbicella borradailei, n. ,sp. (PI. LXIII. fig. 34.) 



Colony massive, rather irregular, covered under the edges by a distinct, transversely 

 waved epitheca. Corallites, 11 — 15 mm. in diameter, eHges raised into broad, padded rings 

 1 — 5 mm. high, somewhat crowded together and distorted, especially on the inequalities. 

 Calices also distorted, 9 — 11 mm. in diameter, 3 — 6 mm. deep, no theca visible from surface 



