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three different divisions of the Tertiary on the Balik Papan Bay : 
Mentawir strata L. sumatrensis var. minor, L. neodispansa 
var. minor, L. glabra, Lepidosemicyclina 
poly morpha. 
Pulu Balang-strata  L. acuta, L. flexuosa, L. sumatrensis, 
(Sungei Blakiu) Lepidosemicyclina thecideaeformis. 
Pamaluan-strata L. aff. formosa, L.? neodispansa. 
The stratigraphical succession thus obtained does not entirely agree 
with the one given by H. Dovvitié. It is true that with us in the 
oldest strata occur simple forms of the type L. formosa, but beside 
these immediately forms of the type O. neodispansa are found, which 
according to Dovuvirré must be much younger. On the Sungei 
Blakin occur then beside each other forms with strongly and feebly 
pronounced skeleton-columns (QO. flexuosa) forms of the type of L. 
sumatrensis, and forms with one single, large, central wart, which 
according to DovviLLÉ should occur in separate horizons. The same 
holds for the youngest strata, the Mentawir-strata. 
It is however remarkable, that in the oldest level the simplest 
forms occur, that in the middle level the number of species is greatest, 
and that in the youngest level, which cannot be much older than the 
dying-out-period of the genus, two minor forms occur, whilst of a 
third species very peculiar variations are found. 
Zoology. — “Observations on the Genus Spirastrella’. By Prof. G. 
C. J. Vosmanr. 
(Communicated in the meeting of March 25, 1911). 
Oscar Scumipr established (1868) the genus Spirastrella for a “new 
species” of Siliceous Sponge, the chief character of which was said 
to be that it possessed an “eigenthümliche Art von strahligen Kiesel- 
körperchen, deren Strahlen spiralig gestellt sind.” We now know 
that that sort of spicules is by no means of rare occurrence, and 
that it does not represent a special form of polyaxons, but of mo- 
naxons; such spicules are now called spinispirae. In addition to these 
spicula the skeleton of Spirastrella is composed of tylostyles or also 
of styles. Since Scumipt described his Spirastirella cunctatrix, various 
authors have mentioned numerous “species”; all in all about 44. 
But of these, ten are to be cancelled at once, either because they do 
not belong to our genus at all, or because they are quite inadequa- 
tely described, so that they are not recognisable. 
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