764 J. STANLEY GARDINER. 



IX. Genu.s Leptoria. 



15. Leptoria gracilis, Dana. 



Dana, p. 261, xiv. 6; Ed. and H., p. 407; Klz., p. 13, ii. 5, ix. 11a— d; Gard., p. 739. 



Four specimens belong to this species. They differ from Dana's description and my own 

 Rotuma specimen in being everywhere more delicate, septa less exsert and rough, and all 

 parts thinner. They show little variation, and that mainly due to the presence of boring 

 animals, all kinds of which appear to love their corallum ; from this cause the fused theca 

 may appear thick, in section hollowed out, and the plates of the columella thick and pushed 

 up so as to reach the level of the top of the theca. The surface is studded with the round 

 holes of a crab, Cryptochirus, but barnacles do not occur. 



Locality. Rather sparsely distributed, especially at Minikoi, mainly reef-tiat and outer 

 slope, a specimen from a shoal near the W. passage of Minikoi, and specimens from Hulule 

 and Goidu. Colour, brown with green lines, where the peristome series occur. 



X. Genus Hydnophora. 



The several species of this genus show perhaps as much variation as those of any other 

 in the collection. I did not, however, study the variability of its colonies in situ, the genus 

 being rare at Minikoi, and I have no notes on the variation of the specimens in the British 

 Museum. Although I have more than 50 specimens before me I am quite unable to deter- 

 mine with any certainty out of all the species mentioned by Ed. and H. and Klunzinger, 

 more than H. microcona. H. maldivensis would appear to be a truly explanate form, 

 but I have explanate and massive specimens of H. lobata below, which as also the lobed 

 forms in places approach H. microcona. There are, however, no intermediates, though all 

 as well as the specimens of H. microcona grew in more or less the same environment. This 

 fact then suggests that of H. microcona we have two real varieties, i.e. explanata and 

 lobata. 



Distribution. The genus is found on any reefs in the Maldives, and we observed it 

 forming considerable masses on the outer slope of Goifurfehendu Atoll. It may hence be 

 an important reef-builder. It varies in depth to 32y"., the deeper specimens very markedly 

 differing from all described reef-forms. 



16. Hydnophora grandis, n. sp. (Plate LX. fig. 11.) 



Colony massive and thick but exceedingly light, edges explanate but coarse, clothed 

 underneath by a thin epitheca. Monticules ending above in fine points or in thin plates, 

 in the colony not more than 6 mm. long, 2 — 3 mm. high, varying from 4 to 9 mm. wide fi-om 

 valley to valley, average about 7 mm. The septa on the monticules number from 6 to 18, 

 the most pointed 6 or 8, those most elongated 14 — 18, mode 10 or 12 ; they are not exsert, 

 slightly granular at the sides, rough edged but not toothed, and appear more distinct than 

 in any other species owing to the lowness and breadth of the monticules ; around calicular 

 centres the septa number 6 or less. There is no definite columella but the septa at the 

 bottom of the valleys bend towards the calicular centres, and may be thickened, while between 

 the lower ends sometimes rough pillars arise, especially where the septa round a centre 

 number less than six. In section the monticules are seen to have the very thin, narrow or 



