( 510.) 
The first five species almost occur in every piece. Head-shields of 
the said Phacops-species are very common, pygidia occur as well, 
and an almost complete thorax (which has not been figured by ScHMipT) 
has also been found. I have named these boulders after this charac- 
teristic species. Equally important is further the presence of the 
Leperditia-species, whose valves, both right and left, are occasionally 
present in large numbers in a single stone; in the unweathered rock 
they are bright brown, weathered nearly white. The mentioned 
Strophomena-species is very plentiful, while especially the two bryozoa- 
species, mentioned next, sometimes give the stone a peculiar appea- 
rance. Though occurring in each of these boulders they are hardly 
perceptible in the unweathered rock; they are together in great 
numbers at the fractured surface, split along the foliaceous “Mittel- 
schicht”, like graceful little white feathers. But the structure of this 
fossil may be more distinctly perceived at the weathered surface of 
the boulders. The other fossils mentioned are found but rarely and 
do not contribute in a great measure to the diagnosis of the rock. 
Besides these fossils, however, remains of brachiopoda are very 
frequently met with, which no doubt are characteristic, though I 
have failed to determine them satisfactorily. Some Phynchonella- and 
Orthis-species are undeniably present among them. One piece also 
contains white, globular and angular erinoid-stems. Also the presence 
of graptolite-remains is most interesting ; these, however, have been 
y 
preserved too incompletely to be specifically determined. 
Of this species of boulders, thus petrographically and palaeontologi- 
cally characterized there are among my material 33 pieces from the 
following places : 
o 
“Noorderbegraafplaats”’, Groningen 2 
“Boteringesingel’, 7 9 
“Noorderbinnensingel ”, EE 1 
“Nieuwe Boteringestraat”’, 5 il 
Between “Parklaan” and ‘“Heerebrug”, ,, 1 
“Nieuwe Veelading”, 5 3 
Jehind “het Sterrebosch’’, 5 1 
“Schietbaan”, A 1 
Café “de Passage”, Helpman 2 
“Hilghestede”, ‚r 4 
55 1 
Between Helpman and Haren 2 
Villa “Edzes” near a alt 
3 1 
Groningen 1 
“Old Collection” 2 
