62 MADKEPORAKIA. 



47, Porites Porto Rico 2. (/'. I'orti-Riconin serunda.) 



[Uir C'uli'bia, I'oiiit Mala Li^'liUiou.si', 15^ i'atlioms, coral sand, coll. U.S. Fish ('(juimissiou, 

 1898-99 ; Washington and British Museums.] 



Syii. " I'ltrites porites forma diraricata Lesueur," \'aughaii, 15ull. U.S. Fish Conimi.ssioii for 1900, 

 (1902), ii. p. 316, pi. ii. figs, ia, il>. 



Description. — The corallum branches at wide angles, 90° and more. The stem and 

 branches are all very thin and delicate, from 6 mm. to 4 mm., which is the diameter of the 

 ultimate branchlets ; these are round-topped and of nearly uniform thicknc^ss throughout their 

 lengtli.s. The forking is slow and seems to take place about every 1'4 cm. apart. The stock 

 is thus open. The lower stems are covered with an ejjithecal film, the living layer being about 

 2 cm. deep. 



The caliclos vary somewhat in size, but from mid-wall to mid-wall appear to be about 

 1 • 75 mm. across. They are very shallow, but distinctly depressed. The walls are low and 

 consist mainly of a stout, nodulated rather than zigzag thread, though here and there this 

 latter character becomes distinct. The wall-thread is also further distinguished by the fact 

 that it is comparatively smooth. Its septal projections are short and stout, and with very 

 finely echinulate knobs at their tips. The symmetry of the calicles is obscured by the more or 

 less imperfect rows of granules along the edges of the septa. It is best seen in those calicles 

 which are drawn out of shape upwards in the direction of growth. Over the greater part of 

 the surface, the internal skeleton is coarsely granular. The columellar tangle is, as a whole, 

 smooth, nodular, and very solid looking, but from its surface finely echinulate granules arise 

 showing gi'eat variety in size and distribution. Sometimes these may be limited to 5 large 

 jiali in a ring, although their typical connections with the septa are obscured; at others, the 

 ring of pali may be only just distinguishable by their size and order from among a number 

 of granules, larger or smaller, scattered apparently without order or obvious relation to 

 the typical calicular skeleton. It is possible that some of them may be homologues of the 

 typical septal granules. 



The section shows a small, open, filamentous axial reticulum, round which the elements 

 thicken enormously into irregular solid masses, obliterating all traces of any regular lattice-like 

 skeleton. 



The designation applied tf) this form by Dr. Vaughan, given above in tlie heading, implies 

 that it is the same coral as that recorded from Guadalupe, in 1820, by Lesueur, a description 

 of which is given above, p. 42, and it will there be seen that the data are insuthcient to allow 

 us to affirm either that they are or are not identical. Eeference to the Table III. will show 

 that branching forms with wide angles of forking are not so rare that they must all be 

 classed together. A comparison of them, indeed, shows that the divaricate forking occurs in 

 many quite different forms. 



