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(left) side the protomesentery 2 is a fertile mesentery of the m- 
type, on the other side a sterile b-mesentery of the B-type. The 
Fig. 7. Cerianthus (?) mortensenii. Diagram of the arrangement of mesenteries. 
protomesenteries 3 are on the left side a sterile B (b) mesentery, 
on the right a fertile one of the M-type. Comparing the arrange¬ 
ment of the protomesenteries in the two other specimens I however 
