^VEST INDIAN ISLANDS PORITES. 47 



grow and bend upwards into the vertical. From the characters of the branching of this stock, 

 we can distinguish it from either of the other two known Antiguan branching forms. Com- 

 parisons of the calicles, and of the sections of the stems, show them all to ))e distinct. 



It is possible that some of the mammillate processes rising up sharply from the dead 

 surface of the basal stem may be fresh growths and illustrate the typical origin of this Inanch- 

 ing form. Cf. the observation under P. Barlados 10, p. 42. 



a. Zool. Dept. 99. 6. 26. 4. 



28. Porites Antigua 2. {P. Antiijum semnda.) (PI. II. fig. 5 ; PI. X. fig. 4.) 

 [Antigua, coll. Gregory ; Biitish Museum.] 



Description. — The corallum ri.ses into low, bushy clusters, the stems under 1"5 cm. thick, 

 forking dichotomously at about 2 cm. apart, the angle being open, but less than a right angle. 

 The terminals are 1 cm. thick and slightly tapering. They appear at times to have been bent in 

 on one side, owing probably to crowding, and then they may fork iiTregularly. The living 

 layer, being 3 cm. deep and less, is consequently broken up among the different branches. 



The calicles are small, 1 mm., sliallow but rather sharply sunk, and subcircular. The 

 walls are pronounced, not fiat-topped but built of the rapidly thickening smooth tips of 

 trabeculae which sideways show as a pronounced denticulation. From above they are seen in a 

 zigzag arrangement, sometimes running transversely as septal ridges, at others irregularly or in 

 two rows representing the tops of the septa of adjacent calicles ; usually very compact and 

 solid. The racUal symmetry of the calicles is confined to these wall-granules. In younger 

 calicles a wall-thread, from which short septa project, is often present ; this quite disappears 

 lower down. 



Within the calicle the pali rise from what appears to be a coarse, nearly solid, columellar 

 tangle. They rise as stout rods, five, sometimes six, with a columellar tubercle or a central 

 fossa. 



The section is very dense. 



There are two specimens of this coral, which fit together to make a good sized stock 

 standing 10 cm. high. It is very unlike any of the other branching forms from Antigua. Its 

 chief characteristic seems to be that the generic characters merely appear in the arrangement of 

 the top edges of the walls, the tops of the septa and pali. Immediately below these, 

 the elements thicken into a very coarse reticulum, which seems i-apidly to solidify. The 

 radial symmetry, even of the interseptal loculi, is very faint, but one of these is frequently 

 abnormally developed, being as large as the central fossa wliich is sometimes visible. Seen 

 laterally, the wall appears coarse, low and irregularly denticulate. 



«.. With a bleached and corroded fragment. Zool. Dept. 99. 6. 26. 5. 



