PLATE XXIX. 



Medusina costata (p. 49). 



Fig. 1. Imprint of lower sides of two specimens on a slab of sandstone, showing the pyramidal 

 cast of the mouth opening and the imprint of the mass of the body. At a the structure 

 indicates the presence of a gonad. (After Nathorst.) 



Fig. 2. View of the lower side of a free cast, showing the central pyramid and 4 radiating ridges. 

 This and other specimens of the same character Nathorst considers to be casts of the 

 gastric cavity, the radiating ridges being the casts of the opening of the mouth. 



Figs. 3, 3a, 3b. Side, base, and summit views of a cast of a quinquepartite specimen. 



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