SrructurE or THE VenTRAL Sac In MASTIGOCRINUS. 
Fig. 6. From distal third, on left edge of sac. 
Fig. 7. From proximal third, showing plates in normal position. ; 
Fig. 8. From proximal third, showing plates disturbed and exposing articular facets. 
All figures taken from 57048, B.M., and enlarged 20 diam. ‘Lhe small number: 
refer to the ridges, as numbered in the text, p. 198. 
The remurgue represents the artist’s first and erroneous impression of the structure. 
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