MADREPORARIA. 777 



a colony does not apparently belong distinctly to one form and one to the other. We have 

 here accordingly both classes of variation, (1) the vegetative, mainly seen in the thickness of 

 the walls, sizes of calices, number and shape of septa and the size of the columella, and 

 (2) the normal, seen in the shapes of corallites, characters of dividing furrows, depth of calices, 

 nature of columella, besides in some of the characters of (1), indeed in most of those which 

 caused Klunzinger to seimrate ehrenbergana and transversa. There is no trace of dis- 

 continuous variation in my specimens, though Klunzinger is probably dealing with it. In the 

 remarks on the variation of the individual organs which I have to offer below, it is certain 

 that I am dealing mainly with the normal, though it is clear that one cannot as yet, with 

 a study of only 21 specimens, draw a line between the variations. Between each form of 

 any organ mentioned I have found nuraei-ous intermediates. 



The colonies are of two indistinctly divided types, («) flattened incrusting, often rising up 

 into rounded hillocks which tend to become loosened, and covered all over with the living 

 tissues, and (6) massive, more rounded, frequently of considerable thickness and always very 

 dense and heavy. Though there are marked exceptions («) certainly approach closer in their 

 other characters to Klunzinger's ehrenbergana and (6) to transversa. The corallites are 

 quite rounded, or even angular or distorted, or crowding over one another; dividing furrows 

 very narrow, not visible to the unaided eye or 1 mm. broad, depth '1 — 1 mm., where very- 

 small a mere flat area between neighbouring calices. Costae never continuous between calices, 

 often not visibly present. Calices varying in shape according to the corallites, theca visible or 

 not, depth from 1 to 4 mm. Septa 24 — 44, mode about 28 or 30, not at all or very little 

 exsert, generally thickened where they join the theca, quite smooth, thin, somewhat distant 

 to very densely crowded, sometimes arched at their sides and upper ends, sometimes flattened 

 above and falling perpendicularly; generally no determinable cycles, I. and II. occasionally dis- 

 tinct and then equal. Columella formed by trabeculae from 12 — 20 septa, one-fourth diameter 

 of calice or scarcely visible, finely papillate or fasciculate above or merely a few twisted 

 trabeculae. Increase by extra- or intracalicinal budding. Fission extremely rare. In section 

 all more or less the same, little apparent variation. 



Locality. The species is fairly common on the reef-flat near the breaker zone and on 

 the Maldive lagoon reefs, but seldom forms very large masses. Loose heads are frequently 

 found on the boulder zone, where there is little or no sand or in hollows between other 

 corals. When split open, their centres usually consist of their own remains, a good deal 

 broken down by boring animals, often with Lithodomus and Gastropods. Their surfaces 

 are frequently broken by the shield-like ends of Pyrgoma and the smaller oval openings 

 of another barnacle in the walls. Generally the extreme forms are less affected than the 

 intermediates. 



42. Orbicella (Leptastraea) bottai (Ed. and H.). (PI. LXIII. fig. 36.) 



Cor. 11. p. 486. Klz., p. 44, V. 9 and X. 13 a and b. Leptastraea inequalis Klz., p. 4.5, v. (i. 



I refer sixteen specimens to this species, with which Klunzinger's second species is un- 

 doubtedly synonymous. The specimens vary greatly in their different parts, and as compared 

 with one another. The colonies are mostly rather flat and incrusting, but there is one large, 

 round one, and one smaller and oval, almost completely covered with polyps. The corallites 

 are round or compressed, and have their edges scarcely rising above the general level, or 

 1 mm. upstanding above the furrows, isolated ones rising to 2 or 3 mm., or on hillocks, etc.. 



