Formations in the Burlington Limestone. 97 
Upper Burlington limestones. It would seem, from these facts, 
that there was something connected with the presence of siliceous 
matter in depositing waters, during the formation of the uppe 
‘beds of the Lower Burlington Limestone, which was unfavor- 
able to the growth and life of the inhabise Crinoids; for, with 
the introduction of the chert deposits, the Crinoids | appear to 
have declined, and finally all of the species became extinct be- 
fore the completion of the dividing stratum of chert above men- 
tioned. A parallel instance is to be noticed in the fact that 
there is a stratum of chert between the Upper Burlington and 
the cee limestones, which marks a similar organic change: 
e 
many undescribed species, which are as : distinetly limited to one 
formation as those here mentioned. 
Some species of Crinoids which are —_ only in the Lower Burlington 
Lime. 
Actinocrinus proboscidialis Hall. |Actinocrinus i Hall. 
multibrachiatus “ superlatus ns 
sexarmatus s brevis . 
i Ss unicornis Owen & Shumard. 
ornatus . araneolus Meek & esgsiomees 
inflatu a Agaricocrinus Henan 
sculptus 4 pee 
discoidens . Megistocrinus Evansii “rise & Feicserd: 
turbinatus 23 Whitei 
papillatus te Platycrinus Frandei Owen & Shumard. 
rmos a 
inornatus « 
lepidus = ye ideus 
aequalis - Burlingtonensis “ 
opusculus cg Prateni then. 
chloris . ornogranulus M 
clarus 6 scobina Meek & Worthen. 
infrequens i verrucosus White 
lucina = regalis 
thoas * eminulus o 
ovatus ig inod . 
ceelatus = pileiformis “ 
gemmiformis “ me oe “ 
bulis . pocilliformis 
coronatus . nucleiformis “ 
i . truncatulus 
ri . exsertus . 
pentagonus ° calyeulus =“ 
ispina “ cavus . 
subaculeatus “ behones tus : 
“ acu ptus 
igs 
Am, Jour, Sci.—Sxconp SERIES, Vou, XLII, No. 124.Jutr, 1866. 
13 
