248 c Christmas Island. 



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

 is a white limestone with a somewhat crystalline texture. The 

 organic contents may be put clown as follows : Lithoth amnion, 

 sometimes encrusted with Polytrema ; numerous foraminifera, 

 including Orhitoides ; and echinoderm spines. 



The foraminifera are — 



Spirolociclma, sp. near asperula, 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. 



Miliolina alveolini/onnis, Brady. 

 Numerous sections of the above species occur in No. 551. 



Polytrema miniaceum (Pallas), and var. tnvolva, 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 LitJwtJi amnion, after the manner of similar 

 specimens we have observed in the material from the coral boring 

 at Funafuti. 



Heterostegina depressa, d'Orbigny. 

 Some occasional specimens were noticed in No. 551. 



Orhitoides {Lepidocyclina) sumatrensis, Brady. 

 This species is common in No. 551. 



Orhitoides {Lepidocyclina) insulce-natalis, 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 Lithothamnion. 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 — 



Miliolina 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. 



