90 VERRILL, SYNOPSIS OF 



numerous small, rough, convoluted, and intricately united 

 trabiculae, with small, irregular openings among them, 

 the free ends of rough papilliform processes forming the 

 surface. Color of the unbleached coral dark brownish 

 black. Diameter of the terminal branches 1 to 1.25 

 inches; diameter of lateral cells .20 to .25; depth .08 

 to .10. The terminal cells are mostly smaller and rela- 

 tively much deeper. 



Locality unknown, most probably Bonin or Loo Choo 

 Islands. Dr. Wm. Stimpson. 



PoCILLIPORIDiE. 



Observations upon the polyps have shown that this 

 family has the structure of the Madreporaria, and no 

 affinity with Milleporidoe and similar Hydroid corals.* 

 The twelve well-developed and regular septa, seen in 

 such species as JP. elongata, I*, stellata, P. plicata, etc., 

 also give ample evidence of their intimate relations to 

 the true Polyps, and are inconsistent with Hydroid struc- 

 ture. Occasionally a cell divides by fissiparity, and in 

 that case has twenty-four septa just before division. The 

 transverse plates have a concentric structure and are often 

 seen incomplete, with a round or oval opening through the 

 centre. It appears worthy of separation from Favositidm 

 on account of the imperforate walls, abundant coenen- 

 chyma and other characters. 



PociLLiPORA GRACILIS Vcrrill, sp. nov. 



Corallum cpespitose, low, and densely branched, the 

 branches slender round, rarely with intervals of a quarter 

 of an inch between the branchlets. The branches and 

 branchlets are dichotomous and diverge at acute angles. 

 The terminal branchlets are rarely a quarter of an inch 

 long, about .08 of an inch in diameter, with obtuse or 

 rounded tips. Cells shallow, .03 of an inch in diameter, 

 or a little less, with a small, prominent columella, and 



* On tlie Affinities of tlie Tabulate Corals, by A. E. Verrill, Proc. 

 of the American Association for Advancement of Science, 1867, p. 148. 



