IQ2 



PLATE II 



Clionolithes radicans, a single cluster of tube 

 casts, X 5 in the substance of the shell ofAtrypa retic- 

 ularis from the Chemung sandstone of Mansfield, Pa. 



The same. A silicified replacement of a tube cluster within 

 the shell substance ofLeptostrophia magnifica 

 Hall, standing in relief on the surface of the valve. From 

 an enlarged photograph, which also shows the casts of 

 the small tubules constituting a proper part of the 

 structure of this shell and through one of which it is prob- 

 able that the sponge entered. From the Grande Greve 

 limestone (Lower Devonic) Gasp^ 



Clinolithes rept an s ; sparse, diffuse tubules in the sub- 

 stance of a shell of Leptostrophia oriskania, Oris- 

 kany limestone, Becraft mountain, N. Y. Greatly enlarged 



