331 The Oligocene OF THE Southern United States 21 



Fossiliferoiis beds of Limboiirg. The fossiliferous beds of 

 Limbourg, being the standard to which all lower Oligocene 

 deposits are referable, have an important place in geological 

 literature. In addition to the work of Dumont, already 

 mentioned, the publications of Nyst,* Hebert.f Bosquet, J 

 Rutot.ll Mourlon§ and Van den Broeck='"^ are important. 



Ostrea ventilabnitn beds. The Ostrea ventilabnuti beds are 

 best exposed in a sunken road which leads from Tongres to 

 Brouk. Near that hamlet the steep sides of the road are formed 

 of lower Tongrian sandy marls. These are concealed by sod and 

 later formations except where a small open cave has been formed 

 by undermining. The roof of this is full of Ostrea shells, especi- 

 ally the species veyitilabrum, but qiieteleti is also fairly abundant. 

 PeHen bellicostatus and Catdmm elegans are common. A number 

 of other species were also observed by the writer, but all except- 

 ing the Ostrea shells are so exceedingly fragile that they fall to 

 pieces even on exposure to the air. To preserve the specimens it 

 is necessary to soak them at once in gum arabic and allow them 

 to dry thoroughly before attempting to transport them. 



M. Vincent, dire(5lor of the paleontological division of the 

 Belgian survey, has identified some 42 species of mollusca from 

 these beds. Among others he finds 



Pinna margaritacea Lara. Area appendiczdata J. Sow. 



* Recherches sur les coquilles fossiles de Hoesselt et Kleyn-Spauwen, 

 province de Limbourg, 1836, Extrait die I\Tessager des arts et des sciences de 

 Gaud. 



t Sur les foss. tert. du Limbourg, etc., Riill. Soc. Gcol. de Fr., 2 ser., 

 t. VI, 1849, p. 466. 



X Recherches paleontologiques sur le terrain tertiaire du Limbourg neer- 

 landais. Amsterdam, in-4°, 28 pp., 2 pL, 1859. {Acad, des set. ttaturelles 

 dA>nsterdam, D. VIII). 



II Description de la fauna de I'oligocene inferieur de Belgique (tongrien 

 de Dumont), Bruxelles, in-8°, 1876, 4 pi. (ire partie seule pub.). {Ann. de 

 la Soc. niatacologique de Belgique, t. XI, pp. 1-67). 



^ Geologie de la Belgique. 2 vol., in-8°, t. I, 1880, t. II, 1882. Liste 

 generale de fossiles. 



** Coupe d'oeil Synthetique jette sur TOligoc^ne Beige, 1S94; and Rutot, 

 Observations stratigraphiques relatives aux terrains oligocenes et quater- 

 naires du Limbourg. Ann. de la Soc. geoL de Belgique, V, 187S, pp. 141-155. 



