2 L Bulletin 24 62 



tained faunas. These collections have not as yet been exhaus- 

 tively studied, but enough is known so that the following general 

 conclusions may be drawn. On Tinsbury creek, near Petersburg, 

 blue, fossiliferous marl is exposed, containing an abundant fauna 

 together with a large quantity of quartz pebbles, derived from the 

 underlying crystalline rocks. From this locality about 75 species 

 have been determined, of which between 13 and 14 per cent, are 

 represented by living forms. On Lieutenant's run, near Peters- 

 burg, the same quartz bearing marls are exposed showing more or 

 less the same paleon'tological characteristics. On Coggin's point 

 Miocene occurs on Ruffin's branch, where they are seen to over- 

 lie Eocene beds. The fauna differs little from that of Petersburg, 

 but contains in addition Pecten clintonius, P. virginianus, P. de- 

 cemnarius and Cardium virginianum. At Evergreen, Miocene 

 beds are again met with of the same general type. Here Melina 

 (Perna) maxillata is common with an occasional P. virginianus ox 

 decemnatius. The beds here also overlie Eocene beds. 



Not a single species characteristic of the Calvert or Chop- 

 tank formation has been found in the above beds. On the other 

 hand, the majority of the species occur also in the Yorktown or 

 Duplin formation. Species which illustrate this point may be 

 mentioned : Ostrea disparilis, O. sculpturata, Chama corticosa, 

 M'utinia congesta, Astarte concentrica , Area scalaris, Pecten ebor- 

 eus and others, 



The above points are therefore irreconcilable with the correl- 

 ation of these beds with the Calvert formation. The basis of 

 percentage of the recent species ; the paleontologic similarity to 

 the overlying beds of the Yorktown formation ; and their strati- 

 graphic position : all point in favor of considering these beds as 

 belonging to the St Mary's formation. With the St Mary's from- 

 ation as exposed at its typical section, these beds agree in their 

 lithological and general paleontological characters. On the whole 

 however, they appear to me to belong to a slightly younger stage 

 than that at the type section. Few of the species are entirely con- 

 fined to this formation in this region. But we may mention here 

 Astarte arata, Area virginice , and Chione dalli. Melina{Perna) 

 maxillata is generally common throughout and is lacking from 

 the Yorktown. Pecten virginianus and decemnarius are almost ex- 

 clusively confined to it, but an occasional specimen is found in 

 the Yorktown. 



