252 Messrs. R. B. Newton and R. Holland on some 



thanks are also due to Professor Molengraaff for granting us 

 the privilege of studying his interesting specimens from West- 

 central Borneo. Finally we may state that our studies of 

 the " Everett " limestones have been greatly facilitated by 

 the excellent microscopic sections prepared for us by 

 Mr. Richard Hall, the assistant-formatore of the British 

 Museum at South Kensington. 



Description of the Foraminifera. 



(a) nummulites. 



1. Nummulites jnvanus, Verbeek, form B. 

 (PI. IX. figs. 1,2,3.) 



Nummulites javanus, vars. A (soloensis), B, C, D, Verbeek, " Voor- 

 loopig Bericlit over Numniulieten, Orbitoiden en Alveolinen van 

 Java&c," Nat. Tijdscbr. v. Nederl.-Indie, 1891, vol. li. pp. 105, 106, 

 figs. 1, 2, 3 ; K. D. M. Verbeek and R. Fennenia, Desc. ge"ol. Java 

 et Madoura, 1896, vol. i. pi. iii. figs. 45-57, pi. iv. figs. 58-68, pi. v. 

 figs. 69-73, and pi. vii. fig. 94, vol. ii. p. 1143 et seq. 



Shell lenticular ; edge somewhat obtuse ; one surface more 

 convex than the other ; sometimes the shell in vertical section 

 appears plano-convex or even concavo-convex ; the majority 

 of the vertical sections show a slight sigmoidal curvature; 

 surface probably smooth, but none of our specimens have 

 been obtained free from the matrix. The " columns," however, 

 do not pass up through the vertical section sufficiently strongly 

 to produce tubercles upon the surface, though there might be 

 slight external markings. The " filets cloisonnaires," or 

 alar prolongations of the septa, are subreticulate, and are well 

 shown in horizontal section in PI. IX. fig. 3. This figure is 

 strictly comparable with figs. 67 and 68 in plate iv. of Ver- 

 beek's work mentioned above ; and it will be seen from our 

 figure that " les piliers sont grenus en coupe," as Verbeek 

 describes them in his Javan specimens. 



The mean dimensions of the Bornean specimens are 

 20 millim. in diameter by 4 millim. in thickness; but in all, 

 or nearly all these specimens, the actual size must have been 

 somewhat greater, because the external surface of the shells 

 has suffered more or less corrosion in the process of fossiliza- 

 tion. There are about 20 turns of the spiral in a radius of 

 10*5 millim. and 16 chambers in \ turn at a radius of 5 millim. 

 The coiling is, however, irregular. The chambers differ con- 

 siderably in size even in the same convolution, though not to 

 the extent apparently shown in PI. IX. fig. 2. That figure 

 is deceptive, as all thin sections of Nummulites cut on the 



