550 ZOOPHYTES. 



GENUS I. PORITES. CaviF.n. 



Poritida polypis 1%-tentaculatis, lineam latittidine non superantibus, zoo- 

 phytis glomeratis et furcato-ramosis, ramis nunquam bene teretibus, 

 apice obtusis. Corolla omnino porosa, cellis paululum profundis aut 

 super faialibus, intus radiatim granulosis. 



Polyps with 12 tentacles, and not exceeding a line in breadth ; zoo- 

 phytes glomerate and furcato-ramose ; branches never neatly terete, 

 obtuse at apex. Coralla throughout porous ; cells shallow or super- 

 ficial, radiately granulous within. 



The Porites are among the most important of reef-forming zoophytes. 

 They are various in their forms and sizes, occurring either as incrus- 

 tations, or closely ramose, or glomerate in rude hillocks or rounded 

 masses. Some of the latter, met with by the author, had a circum- 

 ference of sixty feet. The branches are often coalescent, and some- 

 times into sublamellar forms ; but foliated varieties have not been seen. 

 The cells are never over a line in diameter, and rarely as deep as their 

 breadth. They are either conical within, or very shallow cylindrical 

 (fig. 5), and the septa are acute, and quite thin, or have some little 

 breadth ; but, when broadest, the septa or interstices do not exceed in 

 breadth half the diameter of the cell. Figures 7 to 12, on plate 53, illus- 

 trate the principal forms, while figures 3 a, 5 a, on the same plate, and 

 others, on the following, represent their interior structure. The form 

 in figure 7, is found in the P. favosa and P. mordax; that in figure 8, 

 in the P. compressa, P. lobata, and P. conglomerata ; that in figure 9 ( 

 in most specimens of the P. nigrescens, towards the extremities of the 

 branches; that in figure 10, in the P. punctata; that in figure 11, in 

 the P. fragosa; and that in figure 12, in the P. astrseoides. Within 

 the shallow cell, six points or irregular granules may commonly be 

 distinguished around the central point or pore, and twelve others 

 around the six; and often one of the six, with two of the twelve, form 

 together an imperfect letter V. In some species (P. astrseoides), with 

 deeper cells, there are twelve distinct and nearly vertical lamellae, 

 with a short columella at centre. 



The polyps of this genus were first examined and figured by Le- 

 sueur, and subsequently by Quoy and Gaymard. They approach 

 those of the Alveoporse, among the Favositidse. 



