752 MB. J. STANLEY GABDiKER osT [June 6, 



below by a more or less developed columella, formed by trabeculae 

 from the septal edges. Interseptal loculi deep, closed below by 

 transverse endothecal dissepiments. Septa usually somewhat 

 exsert and well-developed, commonly at least two cycles fusing 

 with the columella. Paliform lobes generally present and well- 

 developed, usually recognizable at least in some parts of a colony. 

 Costse varying in development, generally distinct, but sometimes 

 not recognizable in surface view. Exotheca usually well-developed, 

 often completely filling in the space between the theca of neigh- 

 bouring corallites. Increase by intercalicular gemmation over the 

 costss, where three or more calices meet, sometimes also by 

 fissiparity. 



1. Oebicella aceopora Linnaeus. 



Madrepora acropora, Linnaeus, Syst. Nat., edit. 12, p. 1276 



Madrepora acropora, Esper, Eorts. Pflanz. i. p. 21, pi. xxxviii. 

 (1797). 



Heliastrcea o,cropora, Milne-Edwards & Haime, Cor. ii. p. 477 

 (1857). 



There are two specimens, both incrusting masses, v^^hich 

 correspond closely to the above descriptions. The edges of the 

 calices are free for about 1 mm. in height, while the calices are 

 about 2 mm. deep to the top of the columella and in diameter vary 

 up to 5 mm. The costse and septa are as described by Milne- 

 Edwards and Haime, but the smaller costse are not usually present, 

 and the septa which reach the columella — generally 9-12 — have 

 commonly a very distinct paliform lobe. Increase is usually by 

 intercalicular gemmation, but in three calices of the larger 

 specimen — 10 by 6 cm. — fissiparity is occurring. 



There are two specimens, the first as described above, but the 

 second differing in having rather smaller calices, more delicate 

 septa, and less distinct pali. 



Eotuma ; outer reef. 



The appearance represented by Esper in the lower right calice 

 of fig. 2 is due to a worm boring in the columella. It commonly 

 occurs in many corals, and ultimately results in killing the polyp 

 into which it grows. 



2. Oebicella oeion Dana. 



Orbicella orion, Dana, Zooph. p. 720, pi. xiii. fig. 14 (1848). 



A single lobe from the surface of a colony, which agrees closely 

 with Dana's figures and descriptions so far as they go. The 

 calices are more or less rounded, with distinct free edges, very 

 little raised. There are three complete cycles of septa and a 

 few septa of a fourth cycle are often distinguishable. Of these 

 the primary septa are usually markedly larger and broader than 

 the rest and have well-developed, blunt paliform lobes, which may 

 be simulated by two or three septa of the second cycle. The 



