227 
breite. Schale anfanglich flach, dann allmählig unter einem rechten 
Winkel nach der Ventralseite zu gekriimmt, so dass die Dorsal- 
schale convex wird. Oberfläche mit zahlreiehen feinen, aber deutlich 
runden Rippen bedeckt, deren Zwischenräume durch 2—3 sehr feine 
Radialstreifen angefüllt sind. Ausserdem befinden sich auf dem 
flachen Teil der Schale noch eine Anzahl unregelmässiger, flacher, 
concentrisch angeordneter Runzeln, ahnlich wie bei Strophomena 
rhomboidalis. In der Mitte der Dorsalschale befindet sich oft noch 
eine kleine, aber deutliche Kinsenkung”’. 
The concave ventral valve has not been discovered by Gager either. 
In consideration of my scanty material I was not enabled to make 
certain about the petrographic resemblance between the boulder 
from Spittelhof and the one found by myself; still it seemed to be 
rather great. 
The second and latest writer that has described erratics with 
Strophomena Jentzschi Gag. from Germany is Stotiey (20 p. 136). 
Without mentioning the finding-place (only the district Schleswig- 
Hollstein is given), he mentions two more blocks. The one is composed 
of light-grey limestone, in which here and there vermiform concre- 
tions of glauconite grains occur. Beyond a number of specimens of 
Strophomena Jenteschi Gag. this boulder contains only Orthisina 
plana Pand. The other resembles in a most marked degree the 
preceding one, but contains only a trace of glauconite and the only 
fossil accompanying Stroph. Jenteschi Gag. was Orthisina concava 
var de eBahl: 
To my knowledge this Strophomena. has not been detected in 
erratics from Denmark. 
Only a few years after Gacer, had described the species, J. G. 
ANDERSSON also recorded a number of erratics with the same fossil 
from Sweden. One of them originates from L. Brunnby in the 
parish of Stenasa - in Oeland, one from Källunge Myr in Gotland 
and four from Gotska Sandon. 
All these specimens differ largely from the one of Groningen as 
well as from the German pieces in that they are filled with a 
number of rolled fragments of brown phosphorite and brown 
to black phosphoritic sandstone. This makes them true conglo- 
merates, which induced ANDERssoN to style them Strophomena- 
Jentzschi-conglomerate. Similar blocks have not been recorded either 
by SrorLey or by GaceL, who do not make mention either of any 
phosphorus-content. Neither does my specimen. What typifies 
ÄNDERSSON's erratics, is that some. phosphorite blocks contain Upper- 
Cambrian fossils, viz. Peltwra scarabaeoides Wahlb., Sphaerophthal- 
