UNKNO^VN ATLANTIC OR WEST INDIAN PORITES. 95 



83. Porites West Indies .r. 18. (P. Americana incertm sedis odavadccima.) 

 (PI. V. tig. 7 ; PI. XIV. fig. 5.) 



[British Museum.] 



Description. — The coralhim rises from a short stem, 2 cm. thick in its greatest diameter, 

 and gives rise by irregular dichotomous forking to a cluster of wavy, nodulated stems of 

 very irregular thicknesses, and thickening as they rise. They are mostly erect, but without 

 fusions. They fork mostly so unequally that one, the thicker prong, carries up the stem, 

 while the other stays behind as a small, projecting, perhaps mammillate process. The 

 massive and swelling terminals are mostly flattened, and in the act of dividing up into two 

 or three quite irregularly, but somewhat divaricately. Tlie living layer is about 4 cm. deep. 

 An epithecal film creeps up over the dying edges. 



The calicles are about 1 • 5 mm. in diameter, and flush with the surface excepting where 

 they are passing from the undifferentiated tips to take on adult characters. The walls at such 

 places are thin, raised, zigzag membranes, and surround dark fossje, from the depth of wluch 

 minute pali and other processes arise. Lower down, the wall is merely a faint ridge, every- 

 where thin but irregular, here slightly nodulated, there a smooth filament. The septa are 

 mostly short, and appear to consist of septal granules and pali, either toucliing one another or 

 joined by very short, smooth, thin filaments. They are symmetrically arranged round a large 

 ring of pali, six in number, the directives taking part. These pali surround a large, round, 

 columellar tubercle. 



The colour of the unbleached coral is a light brown. 



The section of the basal stem is somewhat remarkable, on account of tlie enormous size of 

 the axial reticulum, which is very open and delicate, and shows the cross sections of calicles 

 with neat, open, almost petalloid, interseptal loculi, and also on account of the sudden 

 transition of this axis into a cortical layer of radial trabeculce. 



This coral, with its clusters of erect gradually thickening branchings, recalls that described 

 and figured by Dr. Vaughan (see above F. Porto Rico 3, p. 63), but that was a much larger coral, 

 14 • 5 cm. high, whereas tliis is but 9 cm. Its branches were also proportionately thicker and 

 its calicles larger. Fvirther, its stems and terminals were all straighter, more erect, and less 

 nodulated, the terminals dividing less divaricately. The museum fortunately possesses several 

 West Indian Porites with this kind of growth-form, all differing greatly in details. See 

 further Table III. p. 136. 



There are two specimens. 



a, h. Zool. Dept. 1906 1. 1. 2. and 3. 



