104 FOSSIL FAUNA. 



PLATE XLIL— continued. 



Fig. 4. A variety of Siphonia {Jerea excavata, of Michelin), from the greensand of Wiltshire. 



Fig. 5. A siliclfied Siphonla from Saumur. 



Fig. 6. A Ventriculite from a gravel-pit ; the markings are produced by the exposed and 

 partially abraded outer integument, which in perfect examples consists of a regular 

 net-work of subcylindrical fibres. 



Fig. 7, is a transverse section of a Siphonia {Siphotiia pyriformis of Goldfuss). 



Fig. 8. A nearly perfect specimen of a similar fossil. In fig. 7, are shown sections of tubes 

 passing from the periphery to the centre ; in fig. 8, the central aperture of the cavity 

 of the bulb, and part of the stem, are displayed. 



Figs. 9, & 10, are imperfect specimens of Choanites : fig. 10, is a vertical section showing the 

 central cavity and the connected tubes. 



Fig. II, is another example of Siphonia pyriformis. 



Fig. 12, a vertical, and fig. 13, a transverse section, of the same species of Siphonia. 



Fig. 14. A small turbinated calcareous spongite from Switzerland. 



Fig. 15. The appearance of the animal membrane exposed by immersion of the fossil (fig. 14), 

 in diluted hydrochloric acid. 



