248 . Christmas Island, 



No. 551, at summit of cliff at about tlie same horizon as 521, 

 is a white limestone with a somewhat crystalline texture. The 

 organic contents may be put down as follows : Zithothamnion, 

 sometimes encrusted with Polytrema ; numerous foraminifera, 

 including Orlitoides ; and echinoderm spines. 



The foraminifera are — 



Spiroloculina, sp. near asperuhy Czjzek. 



An arenaceous form of Spiroloculina occurs in this limestone, 

 which is perhaps referable to the above species. A similar form 

 was noticed in No. 924. 



MilioUna aheoUniformis, Brady. 

 iN'umerous sections of the above species occur in No. 551. 



Polytrema miniaceum (Pallas), and var. involva, Chapman, nov. 



Some free-growing specimens of the above form are seen in the 

 slide of No. 551. One of the specimens is seen to be encrusting 

 a nodular mass of Lithothamnion, after the manner of similar 

 specimens we have observed in the material from the coral boring 

 at Funafuti. 



JECeterostegina depressa^ d'Orbigny. 

 Some occasional specimens were noticed in No. 551. 



Orlitoides {Lepidocyclina) sumatrensiSf Brady. 

 This species is common in No. 551. 



Orlitoides {Lepidocyclina) insulce-natalisj sp. nov. 

 A fi'agment or so of the above species occurs in this slide. 



No. 841 occurs at the top of the cliff section at Flying Fish 

 Cove, where the rock forms projecting pinnacles by weathering. 

 It is a dense white limestone with some travertin, and composed 

 chiefly of encrusting Zithothamnion. Many foraminifera are also 

 present. Also many polyzoa and a Serpula were noticed in the 

 section. This rock has a more recent aspect than any of those yet 

 enumerated in the foregoing pages. 



The foraminifera are — 



MilioUna alveoliniformis^ Brady. 



Sections of the above form occur in No. 841, associated with 

 other species of the same genus whose specific relationships cannot 

 be easily made out. 



