A. JEJ. Vernll — Corals of the Ge7ius Acropora. 247 



In general appearance this has some resemblance to A. calartxaria 

 ^Br,), but the primary branches of the latter do not coalesce into a 

 Ijasal disk, at least in the type, and its branchlets are more obtuse, 

 shorter and thicker, and the corallites do not agree very closely. 



Acropora fraterna Ver., sp. nov. 



Plate XXXVI. Figure 18. Plate XXXVI B. Figure 9. 



One of the specimens in the Yale Museum labelled as M. paxil- 

 ligera by Dana, differs specifically from another type-specimen, which 

 agrees well with his description and figure. 



This coral forms a large, flat-topped, turbinate clump, covered 

 above with stout, conoidal, subacute branches ; below, it arises from 

 a stout, compact pedicel, 6 to 7 inches (150 to 175"™) in diameter, 

 rapidly Avidening upward. It is formed by large, obliquely ascend- 

 ing, primary branches, which are almost completely coalesced into a 

 thick mass, with only a few submarginal openings, and covered 

 beneath with numerous, rather large (1.10 to 1.30™'"), stellate, 

 immersed calicles, btit without any projecting branchlets nor promi- 

 nent corallites. 



The upper marginal branches are stout, very obliquely divergent, 

 and digitate, more or less coalesced proximally. The upright 

 branches of the central portions are not crowded, elongate-conical, 

 35 to 50""" long, 15 to 25""" in diameter at base, regularly tapered, 

 subacute. 



The axial corallites are rather large, mostly 3 to 3.5™" in diameter; 

 1 to 2™™ exsert, with moderately thick, very porous walls, strongly 

 costulated externally ; septa usually 12, narrow. 



The radial corallites are very unequal ; the larger distal ones are 

 2-3™™ exsert, about 1.5-2™™ in diameter, tubular, scarcely com- 

 pressed, obliquely truncated or labellate, with a dimidiate lower lip, 

 which is not thickened nor incurved, or but slightly so ; inner li]) 

 usually pretty well developed, free, but thin, often entirely adnata ; 

 outer walls strongly costulate, with rows of large pores between the 

 costulie. Septa usuall}' 12, the six primaries rather narrow; the 

 others almost rudimentary. 



Between the larger radial corallites there are manj^ croAvded 

 smaller ones, 0.5 to 1.25™™ in diameter, short-tubular, rather exsert, 

 with thin, costulate walls, and an open terminal aperture, which 

 may be more or less oblique. The larger corallites stand out rather 



