Suburban Geology of Richmond, Indiana. 



293 



drical 



are elliptical, have a long diameter of five 



inches and a transverse diameter of three inches. 

 The siphuncle of these large specimens is lateral, 

 and varies from two to two and a half inches in 

 diameter. 



Insulated as I am with respect to the seats of 

 science, and inaccessible to me as are the appro- 

 priate authorities, I do not know whether the fossil 

 1 am about to describe is already familiar to the 

 paleontologist, or whether it is altogether unique j 

 but as none of my scientific friends, who on visit- 

 ing this place, have seen it, and none who have 

 received casts of it appear to have been acquainted 



Fig. 8. 



similitude of a small Unio f and another, by no means common, 

 having inequilateral valves marked with delicate concentric lines. 

 Except these anonymous ones, and the Strophomena 

 semiovalis, S. deltoidea, and Orthis testudinaria, 

 these shells are very common. The Pterinea is 

 chiefly found in the "marlite;" and indeed, this 

 bed is most prolific of the genera. On breaking 

 open these bivalves we often find them filled with 

 calcareous spar; even the thin Strophomena3 are 

 generally compacted in the same manner. 



Univalves. — One species of Turbo ^ (Monodon- 

 ta?) and this is not common; one species of Tur- 

 ritella, which is still less frequently found ; a sin- 

 gle specimen of a large Conularia quadrisulcata ; 

 five species of Orthoceratites ; the Platyceras ven- 

 tricosum (Conrad;) a Seller op hon, and a fossil 

 which I venture to place here, and call for present 

 convenience, Aulacera. Of these, the orthocera- 

 tites is much the most common. The largest spe- 

 cies I have always found in the "marlite;" one 

 specimen, which as usual is not perfect, is upwards 

 of two feet long, and another eighteen inches long ; 

 some have a diameter of but one fourth of an inch, 

 while the larger ones, which instead of being cylin- 





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I say Unio by way of comparison ) I do not suppose it to be a fresh- water shell 



