228 A. E. Verrill — Corals of the Genus Acropora. 



seems to be to separate the allied forms of this group, rather than to 

 unite them. Still I think it uot unlikely that a larger series of 

 specimens would compel us to unite them in one species. 



Acropora diffusa Ver. See p. 214. 



Madrepora diffusa Verrill. Bull. Mus. Comp. Zool., i. p. 41, 1864. Queleh. 

 op. cit., p. 161. Brook, op. cit. , p. 80. 



Plate XXXVI C. Figure 2. Plate XXXVI F. Figure 16. 



The larger radial corallites in this species are prominent, com- 

 pressed, nariform, standing at about 45° to 60°, not at all appressed. 

 The outer lip is thickened, a little incurved and considerably longer 

 than the thin inner lip. The free part of the inner wall is short 

 but evident, thin. The aperture is oblique and elliptical. Six 

 very narrow primary septa are visible ; the directives are a little 

 wider than the others. The walls are firm but porous and roughly 

 echinulate; the sharp granules are often in costal lines, but usually 

 no distinct costulae are visible, unless on very young corallites. 



The axial corallites are a little exsert and scarcely larger than the 

 radial, with a small calicle (0.75 to l mm ). The primary septa are 

 well developed, but thin. 



Kingsmills Is., co types. No. 1808. 



Acropora digitifera (Dana) Ver. See p. 214. 



Madrepora digitifera Dana, Zoopk., p. 454, 1846. Brook, op. cit., p. 75, 1893. 



Plate XXXVI. Figure 12. Plate XXXVI B. Figure 3. 



Several branches of the type-specimen are in the Yale Museum 

 (No. 430). These were, in part, used by Dana in describing the 

 details of the calicles. The longer branches are 50-65 mm long, and 

 10-1 3 mm in diameter at base, somewhat curved and compressed, pro- 

 liferous, with small normal branchlets on the distal third. 



Near the base the calicles are small and many of them are wholly 

 immersed, deep, with 12 very narrow septa ; others are larger, with 

 a squarrose, short, thick, spout-like lower lip : the upper lip is abor- 

 tive, or nearly so. 



The most fully formed, radial calicles (2 to 2'2 mni in diameter) are 

 on the distal half of the branches ; these are large, strongly squar- 

 rose, or stand neai-ly at right angles to the branch. They are spout- 

 shape, rather prominent, with the lower lip thick, expanded, well 

 rounded, and not at all contracted ; the upper lip is short and thin. 

 They have a distinct star of 12 septa, all of which are narrow except 



