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rock. They are invariably blackish-gray rocks, in which the fossils 
are to be recognized as white spots. . 
Five boulders (Sabang N°. 117, 1907. Alkmaar N°. 286a. 1907, 
and Geitenkamp N°. 187a 1907 Bibisriver N°. 527. 1907, affluent of the 
Bibisriver N°. 738. 1909) belong to the Alveolina-limestones. They are all 
compact, gray limestones with occasional quartz-splinters. They abound 
in Alveolinae, which we refer tothe primitive type. Some are pointed 
and spindle-shaped and must be referred to A. Wichmanni Rutten, 
others are rather ellipsoid and may be classed among A. Javana 
Verbeek. Besides these, small Rotalidae and Miliolidae present 
themselves. Furthermore there are numerous small Nummulinidae, 
more than 5 mm. in length, which belong to Operculina or to the 
Nummulites. They bear a strong resemblance to the forms 
intermediate between these two genera, which are known to us 
from the Eocene Alveolina-limestone of Tandjung Seilor (East Borneo) *). 
Another Alveolina-limestone, probably also a boulder, was found 
on the northern slope of Geluksheuvel (N°. 320. 1907). The 
limestone is considerably discoloured; it contains the same petrifica- 
tions as the boulders described above. We are struck with the irre- 
gular forms presented by many Alveolinae. They are most likely the 
consequence of stunted growth. 
Three grayish-white limestones, resembling the preceding specimens 
very much, were collected on the solid rock of Wilhelminatop 
(N's 707, 709, 712, 1909). Besides very numerous individuals of 
Lacazina Wichmanni Schl. also rests of Alveolina Wichmanni and 
Miliolidae, Rotalidae and small Nummulinidae occur in this rock. 
Although the limestones of Wilhelminatop belong to the same type 
as the boulders from the Lorentz- and Bibis-rivers, the latter must 
take their origin from another source, as the distribution of the 
fossils in the rocks is different; the boulders do not contain any 
Lacazinae, which on the other hand predominate on Wilhelminatop. 
The Alveolina- and Lacazina-limestones decidedly belong to the 
Old Tertiary. 
The purity of these limestones is remarkable, they seldom present 
quartz-splinters. 
V. Nummulina-Alveolina limestone. 
A blackish-gray limestone from a boulder bank near Sabang looks 
at first sight very much like the Alveolina-limestone described 
(Nt 144. 1907). We see, however, in the sections that Alveolinae 
1) L. Rurren. Samml. Geol. Reichsmuseum Leiden (1). X. 1915, p. 10. 
