96 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



Leptastrea immersa Klunzinger. 

 Plate 31, figures ;, la, lb, specimen from Cocos-Keeling Islands. 

 1879. Leptaslnea immersa Klunzinger, Korall. Roth. Meer., pt. 3, p. 47. plate 6, fig. I. 



The following is the original description: 



"Kelche mittelmassig, ziemlich klein (3-4 Mm. breit, 4-5 Mm. lang), tief (2-3 Mm.), 

 rundlich oder leicht polygonal, durch feine enge nicht ganz seichte lineare Furchen getrennt 

 unci wenig (5-1 Mm.) iiber die letzteren erhoben, doch so dass man noch die Mauer selbst 

 etwas vorragen sieht. Septa nicht sehr zahlreich (20-35), ungleich, die des letzten Cyklus 

 sehr rudimemtar; meist sieht man daher nur 18-20 Septa deutlich, wovon 6-10 starker 

 vorspringen. Die Septa sind sehr diinn, sehr wenig gekornt, und ganzrandig, auch unten 

 ohne Zahn. Columella rudimentar, papillos, in der Tiefe compact. Mauern diinn. Sub- 

 stanz zwischen den Kelchen compact, \-i Mm. dick. Interseptal Plattchen 1 Mm. iiberein- 

 ander. Knospung extracalicinal. 



Kolonie massiv, convex, bucklig. Farbe der Polypen grau. Vorkommen aut der 

 Klippe in Kliiften der Brandungszone." 



Some of the septa in Klunzinger's figure show within the calices a shoulder 

 with a concavity of the margin above it, but neither he nor Matthai describes the 

 septal profiles of the type specimen. 



The following is a description of a specimen from Cocos-Keeling: 



Corallum forming incrusting masses, up to 85 by 60 mm. in diameter and 36 mm. thick, 

 upper surface unevenly rounded, slightly undulate; texture relatively dense. 



Calices subcircular, somewhat deformed by crowding, or polygonal; diameter between 

 thecal summits, 2 to 4 mm., 3 mm. about the average for fully developed calices. Margins 

 slightly elevated, up to 1.5 mm., often taller on the proximal than on the distal side (relative 

 to center of corallum). Distance apart from 0.5 to 2 mm., about 1 mm. usual. Depth 2.5 

 mm., nearly the same as the diameter. Intercorallite depressions distinct; low, minutely 

 granulate, subequal, or alternately wider and narrower costs corresponding to all septa 

 extend down the outside of the free limbs of the corallites to the bottoms of the depressions. 

 Corallite walls thick, solid. Pits for attachment of mesenterial muscles distinct on inside 

 of wall in interseptal loculi. fJ 



Outer ends of septa pronouncedly thickened in the walls, forming a pseudo-theca ; 

 inner portions thin, interseptal loculi relatively wide. First and second cycles prominently 

 developed; the primaries and usually all the secondaries, sometimes not all but most of the 

 secondaries, reach the columella. " Margins exsert, very finely, submicroscopically dentate 

 over the theca, with a line of trabecular divergence. Upper part of primaries narrow; below 

 this is a slope toward the center of the calice, then a perpendicular drop to near the level of 

 the columella, where a second widening joins the septum to other septa to form a false columella 

 (see plate 3 1 , fig. lb.) The secondary septa slope more gradually down into the calice than 

 the primaries. The inner margins of the primaries above the shoulder are obscurely and finely 

 dentate; below it they appear entire; the secondaries are obscurely dentate. Often wing- 

 like processes may be observed extending between the primaries and secondaries slightly 

 above the level of the columella; these are probably incipient dissepiments. There are no 

 pali, nor are there any septal spines in the columella area. The septal faces within the calices 

 are sparsely beset with very small, conical granulations; the granulations more prominent on 

 the exsert parts of the septa. The third cycle is uniformly complete, but usually less than 

 half are distinct as thin lamalla; projecting into the calices, the others being indicated as low 

 ridges on the tops of the walls and barely or not at all visible within the calice. Where 

 the tertiaries are well developed, rudimentary quaternaries are present. 



Columella formed by the fused inner edges of the long septa, which become somewhat 

 compacted by stereoplasmic deposit. Papilla; usually not present on its upper surface; on 

 one side of the corallum a few small papilla; may occasionally be seen. 



Asexual reproduction by interstitial gemmation. There is one instance of fission on 

 the corallum. 



Endothecal dissepiment thickish; exotheca almost solid. 



Habitat and color, Cocos-Keeling Islands.— Dr. Wood Jones states in his notes: 

 "A common form; the colonies are irregular lumpy growths; color, usually some 

 shade of yellow or pale brown." 



