Foraminifeval Limestones. 253 



This species is exactly comparable in outline with the 0. stellata 

 of d'Archiac,^ which, however, has rectangular chambers in the 

 median plane and consequently belongs to the Discocycline series. 

 On account of the difference of contour, this form being polygonal 

 rather than discoidal, it was placed in a separate subgenus, Astero- 

 cyclina. As Newton & Holland have shown, however (Joe. cit. 

 supra, p. 261), the more natural grouping of the Orhitoides is with 

 the two subgenera Discocyclina and Lepidocyclina. The earlier 

 known species having rectangular chambers in the median plane, we 

 have named this form, which has the rounded imbricated chambers, 

 distinctively as Orhitoides {Lepidocyclina) murrayana, after the 

 originator of the expedition to Christmas Island which resulted in 

 the collection of these specimens. 



Our specimen has four rays, the contour between the rays being 

 greatly incurved. The chambers of the median plane have straight 

 sides and rounded or concave ends respectively. The chamberlets 

 of the superficial layer are roughly spheroidal, especially towards 

 the centre of the disc, becoming crowded, cylindrical, and greatly 

 flattened towards the ends of the rays. The primordial chamber 

 in our specimen is very large, measuring aV inch ('85 mm.) in 

 diameter; it probably thus represents form A in the dimorphic 

 sense. Diameter of the disc from point to point, f inch (9 "3 75 mm.). 



No. 986. '' From block in raised beach at north end of Flying 

 Fish Cove." 



A limestone, largely composed of a calcareous mud and rolled 

 beach sand with Orhitoides, the latter having been chipped and 

 worn, and afterwards enwrapped in a thick overgrowth of 

 LithotJiamnion, sometimes 4'5 mm. in thickness, which completely 

 envelops all the large forms. (PI. XXI, Fig. 16.) 



The smaller specimens are free from the encrusting alga. The 

 echinoderm fragments, Lithothamnion, GloligerincBy and Amphi- 

 stegin(S may be of more recent date. 



Foraminifera : 



Glohigerina hulloides, d'Orbigny. Eare. 



Amphistegina lessonii, d'Orbigny. Frequent. 



Seterostegina depressa, d'Orbigny. Common. 



Orhitoides {Lepidocyclina) verheeJci, !N"ewton & Holland. Kare. 



,, ,, sumatrensisj Brady. Common. 



,, ,, insulcB-nataliSy sp. nov. Common. 



1 Calearina stellata, d'Archiac, 1846, Mem. Soc. geol. France, ser. ii, vol. ii, 

 p. 199, pi. vii, figs. 1, la. 



