UNKNOWN ATLANTIC OE WEST INDIAN PORITES. 101 



smooth, except where short, stout lobes arise, which takes place where the encrusting base 

 reaches the edge of its supporting substratum.* These lobes are 2 cm. thick where they rise 

 from the base, but they may begin at one* to flatten, and when about 2 cm. high, to fork. 



The calicles, slightly indented and subcircular, are about 1 mm. in diameter, absent on the 

 rounded tops of the lobes which are undifferentiated, flaky-filamentous reticulum. Tlie walls 

 everywhere consist of loose, open uprisings of this reticulum, whicli, when forming a wall, 

 is mostly angularly filamentous, showing thin trabecule, and thin, smooth, horizontal threads, 

 here and there running together into small flakes. The wall-thread running in this reticulum 

 is often incomplete, frequently has a pronounced zigzag. Its trabecular elements rise all over 

 the surface as thin smooth rods, swelling into finely ochinulate granules. The septa have this 

 same character as they project from the reticular walls. The pali are everywhere well 

 developed, as is also the central tubercle when present. This latter is, however, frequently 

 absent, and instead, a small, deep, open fossa is conspicuous to the naked eye. 



In sections the trabeculsc are seen to be flaky beneath the surface, and running 

 continuously as twisted interrupted lamellae. The colour of the stock is blue-grey, with the 

 finely echinulate tips of trabeculai, septa and pali as whitish specks. 



. This coral has other interests besides its colour, on which see remarks on P. Barbuda 1, 

 p. 50, and note on p. 143. 



One specially interesting problem relates to its method of growth. The larger part of the 

 specimen is encrusting, but it sends up short processes which begin to fork. The question 

 arises as to whether tliis encrusting portion is only a base of what would ultimately have 

 been a branching Porites. It certainly looks like it, not only in the fact of the thick lobes 

 beginning to fork, but also in the facts (1) that the tips are of undifferentiated streaming 

 reticulum, obviously in rapid growth, and such as is seen at the tips of most branching forms ; 

 and (2) That the character of the skeletons of the calicles, a loose, open, foaming or tossing 

 reticulum, almost baffling one's powers of description, is quite typical of branching Porites, but 

 is not at all typical of the encrusting and massive forms — cp. the astrseoid group. 



If this reasoning is correct, it brings the specimen still nearer to the blue branching form 

 P. Barbuda 1, with which it has one other character in common, namely the deep circular 

 fossaj. On the other hand, the branches are veiy different in shape and thickness, and the 

 characters of the calicles differ in their skeletal elements. 



Although there is no record of the locality of this coral, its characters proclaim it as 

 belonging unmistakably to the West Indies. See further Table III., Ea and E6. 



a. Zool. Dept. 1906. 1. 1. 10. 



* In this case, a chip of a brick, and most of the processes seem to arise where the corallum is 

 flowing over one of the edges of the brick. 



