FLORIDAN PORITES. 71 



Group v.— FLORIDA AND FLORIDA REEFS. 



56. Pontes Florida l. (P. Florida: prima.) (PI. XII. fig. 2.) 

 [Tampa Bay, Ballast Point (Miocene) ; British Museum.] 



Description. — The coiallum rose on a stem about 2 cm. thick, and eariy divided into an 

 irregular whorl of 3 or more branchlets, the individuals of which bend up immediately into a 

 close cluster, and become the new stems. They vary greatly in thickness, from 2 cm. to 1 cm. 

 These again, when they have room, divide into fresh whorls, branchlets from neighbouring 

 whorls fusing together. Where there is no room for development, branchlets may be early 

 aborted, and persist only as slight excrescences, or as mammillate processes. The edges of the 

 living layer, which was at least 9 cm. deep, tended to creep down over the dying basal stems. 



The calicles were distinctly depressed, and about 1 ' 25 to 1 • 5 mm. in diameter. The walls 

 appear to have consisted almost entirely of smooth, wavy flakes, not very porous, nor very 

 much incised laterally, the septa starting as very fine thin points standing out rather sharply 

 and suddenly from the edges of the flake, with only slight incurving between them. These 

 shai-p, thin septa seem seldom to have been free, but curved round irregularly to join the 

 wavy flakes which rose in the calicle as the columellar tangle. The symmetry seems to have 

 been entirely confined to the rings of rounded interseptal loculi. 



In the section, very thin, but fairly regular trabecules can be seen, but the tliin, wavy, 

 lamellate, horizontal layers are very marked. 



This specimen is a silicified Miocene fossil, which presents morphological featvues of very 

 great interest. The details are difficult to obtain, but what can be made of its growth- 

 form shows traces of an irregular whorl formation already noted, as perhaps consisting of 

 three prongs, e.g. P. Belize 1, p. 67. Here they might be due to the terminal swellings, 

 dividing not into 2, but into 3, 4 or 5 prongs, which then bend up into the vertical, perhaps 

 fusing with those of neighbouring whorls. 



This is again one of the few branching Poritcs at present known with the horizontal 

 elements of the skeleton so markedly lamellate, that it shows in the structure of the calicles at 

 the surface (cf F. West Indies x. 17, and PL V. fig. 5). I assume that the surface exposed was 

 the original true surface ; it certainly looks like it, inasmuch as each calicle still shows as a 

 depression. 



It would certainly be of inteiest to search among the living Forit.es in the neighbourhood 

 of Tampa to find if this remarkable foim has any survivors. Such characters as these would 

 be easy to recognise. 



a. Geol. Dept. E. 2343. 



