766 



CHALMER L. COOPER 



Ordovician 

 (Generalized section) 



Silurian 



c— s 







<"-*.! 



^s-==^j^^?SS 







'=^==^:='= Richmond 



z 

 < 







c-^l 



! — ' — : _ 



t- 



c-^ 



I ■ 1 =tr 





c — ■ 



r^^=^=^ MAYSVILLE 



z 



: 



i-±r.lzn-j 



- i 



c-^^ 



t^^=^-=^= 





^'^•=^- — ^ -^ Edfn 







c~^i 







Devonian 



Hamilton Beds 

 , Rock Glen, arkona.ont 



(section by STAUFFER.iaiS) 



9 Drepanella clarki 



8. Masticobolbina typus 



7 bonnemaia rudis 



6 Zycosella postica 



5. Mastioobolbina lata 



4 Zycobolbina emaciata 



3. Zyoobolba decora 



2 Zyoobolba anticostiensis 



I Zyoobolba erecta 



UPPER HUNTON group 



arbuckle mts.Okla. 



(section BYREEDS,I9I|) 



Shale 



I5=g Limy ShalE 



^ [ Fissile Shale. bk. 

 1 Coal 

 Unoerclay 

 Sandy Smalc 

 Sandstone 



Black ShalC 

 Dolomite 

 red Shale 

 Shaly Lime STONE 

 Limestone 



— ►OSTRACOOE HORirON 

 A- ABUNDANT 



C- Common 

 R-Rare 

 X- Barren 





Fig. 2. — Graphic sections of the rock series of the Ordovician, Silurian, and Devonian 

 periods showing the stratigraphic distribution of ostracodes. 



from many localities, though the latter is, of 

 course, a very necessary work." This still 

 seems to be a good admonition, and I add 

 my own strong appeal for additional strati- 

 graphic work on some of our less perfectly 

 known horizons, the correlation of which are 

 important to the petroleum geologist. These 

 horizons are found in the Lower Silurian, the 

 Upper Devonian, the Lower and Middle 

 Mississippian, and the uppermost Missis- 

 sippian (Mauch Chunk). The latter may 

 yield information on the confusing problem 

 of the age of the Stanley-Jackfork series of 

 Oklahoma and Arkansas. 



OSTRACODE ENVIRONMENTS 



The study of living ostracodes shows their 



distribution to be world wide and that they 

 seem to be able to thrive under more adverse 

 conditions and are probably less sensitive to 

 rapid changes in environment than most in- 

 vertebrates. The poor swimmers live in the 

 bottom oozes, some exist in the foul waters 

 of sewers and others in sulphur water and in 

 hot springs. They are also known to be al- 

 most unlimited in the depths at which they 

 may exist. Yet ostracodes react to environ- 

 mental influences, as do other organisms, 

 but, due to their free swimming habit, and 

 due to the scattering action of waves and 

 currents, their carapaces may be found in 

 rocks formed under conditions adverse to 

 the existence of the animal. 



Therefore it is not surprising that fossil 



