74 MADREPORARIA. 



the calicles differed as mucli as tlie growth-forms. Their mctliods of forking, the shapes of the 

 terminals, are all different. We confidently claim these as two distinct Floridan Pontes, which 

 must claim attention on their own account, and can no longer be lost sight of as accidental 

 variations of the form called P. furcata, by Lamarck. On this last coral see below, p. 82. 



GO. Porites Florida 5. (/'. Florida: qninta.) (PI. III. fig. 9 ; V\. XI. fig 2.) 

 [Florida Eeefs, coll. Agassiz and Thomson ; IJritish Museum.] 



Description. — The corallum rises as tliin, cylindrical stems, of uniform thickness, slightly 

 over 1 cm., tlie lower portions being sometimes thinner than the upper. The forkings take ])lace 

 some 4 to G cm. apart, and between them the stems are usually slightly curved, each point 

 of curving looks as if it might represent an aborted attempt to fork. The foi-king is at I'airly 

 wide angles, the stock being open, and with long, tliin, straggling branches. The two prongs 

 of each foik are unetpial in size; the thicker one seems to be but slightly deflected from the 

 line of growth, the tlunner one to stand out from this line as a l)ranch. The living layer is 

 5 cm. deep. The tips of the branchlets are round. 



The calicles are subcii-cular, from middle of wall to middle of wall, 2 mm. across, with 

 open fossa 1 • 25 mm. The fossse make the calicles conspicuous. Near the tips the wall 

 shows along the edge as an incomplete zigzag thread, thin, irregular, and giving off septa, tliin, 

 short, and ending in frosted granules. From the base of the fossa, small frosted granular pali 

 arise, with here and there a central tubercle. This character of the skeletal elements extends 

 some distance down below the tips, where the calicles open in the central, reticular, lamellate 

 stroma. As the coral thickens, however, the skeletal elements also thicken, until the thin 

 thread and small granules are purely superficial, and scattered on the surface of broad, solid, 

 smoothly granular, or nodulated walls, or on a solid nodule-like columellar tangle, which fills 

 the base of the fossa, leaving the interseptal loculi as 12 deep, elongated, and very in-egular 

 pits. The fossae gradually get shallower, and the thick septa stouter and longer, until they 

 meet irregularly together and with the pali, on the surface of the solidified columellar tangle. 



The section shows the axial reticulum, of thin skeletal elements, surrounded Ijy a 

 peripheral portion, showing no conspicuous, horizontal, or radial elements, but simply as a 

 dense, irregular mass, of large glassy nodules fused together, and with pores and cavities 

 between. 



This Porites is remarkable for its scanty, divaiicate branching. It differs from all similar 

 stocks which open out by wide forking ; see, for instance, P. Cura^oa 1. For the known 

 divaricate forms, see Table III. p. 136. 



The sudden thickening of the skeletal elements just below the thin surface filigree is a 

 phenomenon already noted, but with different results in the aspect of the calicles, see e.g. 

 P. Florida 2 ; see also P. Bennuda 1. (See p. 143, Appendix to Table IV.) 



rt. Presented by Sir John Murray, K.C.B. Zool. Dept. 91. 2. 3. 15. 



