61 Olsson, Neocene Fossils 



town, the Choptank being considered as absent. These for- 

 mations occur as broad concentric bands, the innermost naturally 

 the oldest. At Petersburg the Miocene rests on crystallines, and 

 on Eocene near City Point and elsewhere. 



In the James rives valley then, commencing at the mouth, 

 the yellow fossiliferous sands first met with, are considered as be- 

 longing to the Yorktown formation. Below these yellow sands 

 are blue clay marls which are divided by Clark and Miller in- 

 to the Calvert and St Mary's formations. It is with these blue 

 clay marls that I wish to deal. Hence formatter of discussion, 

 the Miocene in this valley may be divided into the lower blue 

 clays and the yellow sands of the Yorktown formation. 



A fact which early impresses itself upon a worker in this val- 

 ley is the great paleontological similarity which the different beds 

 present. The fauna of the blue clays, although different in de- 

 tails from that of the Yorktown sands, still shows close relations. 

 A still greater difficulty is encountered, if a further division is at- 

 tempted. In the report above referred to, the Miocene beds at 

 Petersburg, on Coggin's point and in the vicinity of City Point, 

 are placed in the Calvert formation, but I will attempt to show, 

 there is no paleontologic reason which warrants such correlation. 



The fauna of the Calvert formation is rich in species which 

 are distinctive, such as Ostrea percrassa, Pecten humphreysi, Pli- 

 catula densata, Corbula elevata, Cytherea staminea, and others, to- 

 gether with a host of gasteropods, of which we may mention, 

 Turritella indenta*, Fossarus dalli and Ecphora trisulcata. In ad- 

 dition, we may include species which commence in the Calvert 

 and extend up into the Choptank, but not into the St Mary's. 

 Representatives of this class are Pecten marylandicus\ \ Pa?iopea 

 whitfieldi Calliostoma aphelium. It is to be noted that none of 

 these shells occur in the so-called Calvert beds in this valley. 



Rather complete collections were made at Petersburg, Cog- 

 gin's point and at Evergreen because of the interest of their con- 



* Turritella bipertita was described by Conrad from Petersburg. This 

 shell is often considered as a variety of T. indenta. However, these 

 shells are not exactly conspecific and hence not available for correlation. 



^Pecten tenuis H. C. Lea, described from Petersburg is united by 

 Dall with P marylandicus. I have seen the type in the National Mu- 

 seum and consider it the left valve of P. virginiatius Conrad. Vaughan 

 has recorded P. marylandicus and Calliostoma aphelium from the Mark's 

 Head marl, Ga. , which he refers to the Calvert. 



