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evidently serves to support the piston cartilage whilst in use. Artic- 
wlated dorsally with the median ventral on each side is the relatively 
short pointed rod-like styliform (processus spinosus, STY.C.). It is 
evident then that in Geotria australis the piston cartilage and teeth, 
the median ventral and possibly the anterior dorsal are all much more 
strongly developed than the corresponding structures in Petromyzon, 
and correlated with this is the relatively enormous development of 
Fig. 11 (X 1). Side view of Skeleton of Geotria australis. 
Fig. 12 (x 1). Ventral view of head skeleton. 
Fig. 13 (x 1). Dorsal aspect of anterior dorsal cartilage. 
Fig. 14 (x 1). Sagittal section of anterior dorsal cartilage. 
Fig. 15 (X slightly over 2). The piston, median, ventral and styliform cartilages 
in side view. 
Fig. 16 (x slightly over 2). Ditto in front view. 
Fig. 17 (X slightly over 2). The piston and median ventral cartilages from 
the dorsal aspect. 
the buccal funnel with its numerous teeth and possibly also the exis- 
tence of the huge distensible gular sac. 
