216 Christmas Island. 



The septa occur in three complete cycles, and there is one order 

 of the fourth. The columella is from 2 to 3 mm. in diameter. 



The costse are ygyj long, and can be traced out through the 

 compact exothecal tissue. 



Distribution. — Christmas Island. 

 Fossil : 



1^0. 996. Erom limestones of the inland cliff, on the 

 south coast ; alt. 200 feet. 

 ? No. 903. Cast of probably the same species, from the 

 sea-level on the east coast, above basalt 

 and volcanic agglomerate. 

 Figure. — PL XIX, Fig. 3. Part of transverse section across 

 ^0. 996, X 2 dia. 



Affinities. — This species is characterized by the large size of the 

 exothecal areas, which are wider than in any other species of 

 Orhicella known to me. The better specimen was collected from 

 the inland cliffs on the south coast, and may indicate an outcrop of 

 the limestones of the central nucleus at that point. 



Orbicella pleiades (Lamarck), 1816. 



This well-known East Indian species is represented by several 

 specimens, viz. : — 



1^0. 122. Top of the sea cliff, east coast. 



]S"o. 978. Limestones of the inland cliff; alt. 200 feet. East 



. coast. 

 JS'o. 353. On the road, 212 chains south from "West White 



Eeach ; alt. about 450 feet. 

 1^0. 867. Foot of first inland cliff, north coast ; alt. 50-60 feet. 

 :N'o. 212. Foot of the inland cliff, south end of Flying Fish 



Cove ; alt. 50-60 feet. 

 1^0. — . Limestones of the sea cliff, Rocky Point. 



The specimens have the corallites more closely packed than in 

 the specimen shown in Ellis & Solander's original figui'e ; but they 

 agree in essential points with the species as generally accepted. 

 The corallites are circular, and from 2 to 3 mm. in dia. ; the septa 

 in sections are usually twelve in number, but some representatives 

 of an incomplete third cycle occur. 



Orbicella, aff. quadrangularis (Edwards & Haime). 



The collection includes a well-preserved fragment of an Orlicella 

 with large subquadrangular corallites, distinct calicinal edges, well- 

 marked costse, narrow zones of very coarsely vesicular exotheca, 

 and septa which are thick near the walls and become thin near the 

 columella. In these respects it appears to be a member of this 

 species, of which I have not seen either figures or specimens. 



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