716 J. W. BEEDE 
northern-main marine part of the basin were somewhat more con- 
centrated than at its southern shore. 
OUTLINE OF FAUNAL HISTORY 
One of the most striking features of the Kansas Anthracolithic fauna 
is the great range of a relatively large number of species. In regions 
of instability of the earth each successive change of physical con- 
ditions brings in new faunas, tending to eliminate their predecessors, 
and bringing about more rapid and complete faunal changes than in 
interior regions of continental stability. In these latter regions the 
effects of these crust movements are minimized and their effect 
upon the faunas is proportionally less marked. Consequently one 
accustomed to the study of the faunas of marginal continental deposits 
may easily underestimate the value of the less complete faunal 
changes occurring in rather remote epicontinental basins. 
In the regions of great instability it is rarely, if ever, that species 
show their whole life-history, from its inception to its natural termi- 
nation, in an unbroken succession of rocks. In an interior region, 
like the Kansas basin under discussion, persistent species do occur 
exhibiting this life-history fairly completely, and are significant of 
the lapse of time represented by the deposits. Many of the forms 
which are so persistent in the Kansas rocks, especially among the brach- 
iopods, represent the latest stages of the life-history of their genera 
or families which rarely, if ever, give rise to new phyla, since they have 
passed their culmination and entered upon their decline. They are 
therefore not to be expected to give rise to many new forms under 
ordinary conditions (in the higher deposits) and, having largely lost 
their adaptability, perish under untoward conditions. Under this 
class of organisms come the Productidae, Strophomenacea, and Orthi- 
dae, and the genera Seminula, Cleiothyris, Hustedia, Ambocoelia, 
Spirifer, and Pugnax, which are unknown above the Permian. 
Nearly all these groups have their maximum development in the Penn- 
sylvanian or earlier deposits. Among the bryozoans this is still more 
strikingly true. The Fistuliporidae, Batostomellidae, Rhabdomeson- 
tidae, Fenestellidae, and Acanthocladiidae disappear before the 
initiation of the Mesozoic, and nearly all of them have culminated 
before the beginning of the Permian. 
