614 



GEOLOGY 



and new and curious forms appeared. The blastoids had their 

 climax here so far as numbers of individuals are concerned, although 

 there was greater generic diversity in the Osage faunas. The 

 leading genus, Pentremites (Fig. 432), was so prolific in individuals 

 in some beds as to give rise to the name Pentremital limestone. A 

 swift decline seems to have followed this climax, and the beautiful 



Fig. 433. Characteristic Genevieve (Upper Mississippian) Fossils: a, Emlo- 

 thyra baileyi Hall, a small foraminifer, much enlarged, abundant in tin- 

 Bedford limestone of Indiana, and often mistaken, in the past, for 

 an oolitic concretion; 6, Archimedes swallovanus (Hall), a bryozoan 

 having a peculiar screw-like axis for the support of the colony, c-h, 

 brachiopods: c, Spiriferina spinosa (N. and P.), a genus which devel- 

 oped from Spirifer, and has its greatest development in the late 

 Mississippian and Pennsylvanian; d, Seminula subquadrata (Hall 1 , a 

 species closely related to Pennsylvanian types; e, Spirifer increbes- 

 cens Hall, a species characteristic of the later Genevieve faunas: /. 

 Eumetria marcyi (Shum.), a representative of a genus abundant in the 

 Genevieve faunas. It was present in the Kinderhook, but has not been 

 found between the Kinderhook and the closing stages of the ()sa^e; 

 g, Productus fasciculatus McCh.; h, P. marginicinctus Prout; i and /, 

 pelecypods: i, Schizodus chesterensis M. and W.; /, Conocardium />>'nf- 

 tenanum Hall; k-m, gastropods: k, Bellerophon sublin-ix Hall: /, 

 Pleurotomeria nodulostriata Hall; m, Eotrocus concanix Hall. // ami <>. 

 cephalopods: n, Orthoceras annulato-costatum M. ami \V., one of the an 

 cient type of straight cephalopods, occasional species of which per- 

 Paleozoic; ' 



sisted to the end of the Paleozoic; o, Goniatites kcntnckii'nx/'x S. A. M 

 The goniatites reappeared in the Genevieve faunas, though absent from 

 the Osage. 



