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| Vlerk, I.M. van der. |
| There was one great drawback to the decision of the commission for editing this jubilee volume in honour of Prof. Martin in the form that is here shown. It was namely impossible to call in the help of the most competent person for compiling the chapter on the mollusca. One cannot request a scientist to contribute to the celebration of his own jubilee. That I finally decided to undertake this work, that ought to have been done by Prof. Martin himself, is owing to the fact that I was in a better position to learn the opinions of Martin than any other, as keeper of the museum in which nearly all mollusca described by this still active worker are to be found. For this help, though it was given inadvertently, I wish to express my sincere thanks to my much... |
| Tipo: Article / Letter to the editor |
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| Ano: 1931 |
URL: http://www.repository.naturalis.nl/record/505678 |
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| Geyn, W.A.E. van de; Vlerk, I.M. van der. |
| Some years ago we received a collection of foraminifera-bearing samples from Dr. H. K. Kugler and Dr. E. Lehner for examination, in sequence to the collection of larger foraminifera already examined from Central Falcon (Venezuela). (See Nettie E. Gorter and I. M. van der Vlerk, L.G.M., Dl. IV, afl. 2, 1932, p. 94—122). The material from Trinidad is very rich in representatives of the Orbitoididae family. On a closer study of the different genera of this family, for which the large collection of Indian and European Orbitoididae in the National Geological Museum in Leiden provided ample material, we observed that for the determination of genus the interlocular canalsystem is the most important feature. In the Orbitoididae the plasma is conveyed through the... |
| Tipo: Article / Letter to the editor |
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| Ano: 1935 |
URL: http://www.repository.naturalis.nl/record/505742 |
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| Vlerk, I.M. van der. |
| The plates I—XI contain illustrations of all the skulls and horn-cores of Bovidae from the Quaternary of the Netherlands, brought together in the National Museum of Geology at Leyden, Holland. They were all photographed with the occiputs vertical or what is thought to be vertical. They are described in the same order as figured. On the plates I—V are represented the skulls and horn-cores of the domesticated cows. Four races are distinguished among them: the brachyceros-race (fig. 1—25), the frontosus-race (fig. 26), the primigenius-race (fig. 27—41) and the trochoceros-race (fig. 42—46). The brachyceros-skulls and horn-cores have the following characteristics: a sharp angle (30°—50°) between the plane of curvature of the horn-cores and the horizontal... |
| Tipo: Article / Letter to the editor |
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| Ano: 1942 |
URL: http://www.repository.naturalis.nl/record/505932 |
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| Gorter, Nettie E.; Vlerk, I.M. van der. |
| Dr. H. G. Kugler, chief geologist of the North Venezuelan Petroleum Company, at Puerto Cabello, entrusted us with the examination of a collection of larger foraminifera, selected from material collected by the geologists of this Company in Central Falcon. Dr. A. Senn kindly added material that had already been collected from the same region by Prof. Dr. M. Reinhard and Dr. M. Blumenthal. The material thus combined should give us a clear picture of the distribution of the larger foraminifera in 7 stages of the Tertiary in this Venezuelan region. We are very much indebted to Dr. Kugler not only for entrusting us with this material, but also for the constant aid given us during the investigation. We also wish to thank Dr. A. Senn, Dr. W. T. Keller and Dr. E.... |
| Tipo: Article / Letter to the editor |
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| Ano: 1931 |
URL: http://www.repository.naturalis.nl/record/505624 |
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