234 



Helden tlie fauna resembles closely lliat of a moderately deep sea, 

 wliile tlie renmins of Macruridae, occurring in the material of 

 Liessen, originate from deep-sea forms, so that here we have to 

 assnme a greater depth of about 1000 m. This conclusion is in 

 accordance with the results of the inquiries of the Government Institute 

 for (he Geological Exploration of the Netherlands: the boundary-line 

 between tlie contiiienlal and the marine Miocene runs about via 

 Swalmeii ; the lignite formation occui's near Melick-Herkenbosch and 

 Vlodrop, while in the prolile of boring 21 the lowermost layers 

 of the Miocene are marine, and the up|)er layers display a liu)nic 

 facies. ll seems to me (iiat a closer inspection of material from the 

 Groote Slenk, southwest of the Peelhurst, woidd be very interesting. 



The lerliary fauna of this region ditfers from the recent fauna of 

 the Norlh-Sea: on the one side forms occur that inhabit greater 

 depths than those living in the North Sea at the present day, such 

 as Scopelidae and Macruridae, which occasionally occur at iiigh 

 latitudes in the Atlantic Ocean; on the other side the tertiary fauna 

 comprises genera such as Deiitex, Centropristis and Serranus, now 

 li\ing at lower latitudes. In my judgment the occurrence of the 

 latter points to a change of environment, which is to be ascribed 

 either directly to a ciiange of climate, or to other conditions, e.g. an 

 altered direction of the oceanic currents. 



In conclusion I wish tot express my warm thanks to Prof. Dr. 

 J. H. BoNNioMA for kindly placing at my disposal the material in 

 the Geological-Mineralogical Institute of the State University of 

 Groningen. 



