10 JURASSIC RHYNCHONELLIDS 
obirita from the “ Renggert Marl” and R. vivelensis and R. subvariabilis from the 
upper Oxfordian and upper Kimmeridgian respectively were probably attached to 
algae during life. This is suggested as the normal mode of existence but does not 
preclude occasional specimens being drifted considerable distances and thus account- 
ing for the occurrence of rare species such as subvariabilis, as suggested by Ager. 
T. obtrita and R. rivelensis occur in such abundance that it seems unlikely that they 
/ 
y 
( 
t++tetetteerettt 
++eettt¢rtrt+ t+ 
si 
° Hannover 
= 
++ t+++t+t t 
t++t+tett t+ + t+ 
++tettett t+ + 
++++ e+ e+ ¢ + 
pe bo beet eo 
+ 
ES aaa | 
4 
Erlangen ° 
Tubingen °* 
Munich 
— 
SS 
\. 
++ tet 
+ 
+++ + 
++ +t t+ 
\ 
° Bordeaux 
+teertetee it 
t++eeet 
+ 
+ 
+ 
fe 
+ 
a 
+ 
fe 
ip 
ie 
+ 
+ 
ze 
+ 
+ 
+ 
DS 
yee 
\q’e 
Mi 
Pg Se Nb eS ty th ode, ee 
+ 
oie Sts ath 
fp gt 
] 
5 
+ 
+ 
+ 
+ 
+ 
+ 
fe 
+ 
+ 
+ 
+ 
+ 
+ 
fu 
+ 
+ 
+ 
oo 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
Fic. 2. The solid black area represents the outcrop of the Callovian-Volgian ; this informa- 
tion is taken from the map commissioned by the World Geological Congress of 1881. A 
generalized palaeogeography of the Oxfordian-Kimmeridgian (after Kuhn, 1953) is shown 
with the land areas ornamented with crosses. 
