I'iir. 404. Pi \\-SYI.VA\I\\ MARINE FAUNA: o, Euparltyrriniis MiiKtxtcr M. 

 id (I., ;i rrinoid with biscrial arms; b, Fnsnlina xcrulicax Say, a foraminifer shell 

 in places makes up considerable l)cds of limestone, c-p, brachiopods: c, 

 rod net us iu-br<ixtrnxis Owen; d, Productus coslatiix Sow.: e, Snninula aryntra 

 Shep.), a spire-bearing common Carboniferous species;/, Lin^ula uib/iul,i Cox, a 

 >reseutati\ e oi' a gi-nus which persisted from the Cambrian to recent times; g, 

 Iiixtrditi niormoni ( Man .); h,Sf>irifcr camrr<ilns Mort., a characteristic member of 



iVmisylvanian fauna; /, J'rodm-tns xynnnclricHS McCh.;_/, Derbyia <T.;\>.; M 

 and II.); k, Entfldca hcmiplicala (Hall); /, Pugnaxuta (Marc.); m, Dichisnia Iwidi-ns 

 (Mori . ) ; n, M<'< blla slriatocostala (Cox); o, Clwmics zrannlifcra Owen; p,Sf>irifcrin,i 

 tettfuckiensis (Shum.). r, Allorisma snbcuneata M. and H. q-t, pelecypods: q, 

 Monopti-ria lon^ispina Cox; 5, Myiilina rccnrcirostrix M. and \V.; /, Aviciilopcctfti 

 occidfiitiilix Sluun. H-X, gastropods: u, Worthenia tabulata (Con.); , Meekospini 

 pt-nii :i!d (M. and W.); w, Bcllcrophon pcrciirinutiis Con.; .v, Xatit-opxix altoncnxis 

 (Mi ( 'h.); y, 3, and zz, cephalopods: v, Temnoekettus forbenontu ( McCh.); z, Ortho- 

 ceras cribrosum (iein.; zz, Paralcgoceras newsomi Smith; .v.v, Pliillipsia major Shum. 



Map work. No reference to map work has been made since that at the close 

 of the chapter on the Ordovician, p. 387. Experience has shown that if the prin- 

 ciples of stratigraphy, as illustrated by the Cambrian system, are well developed, 

 further map work may be deferred to about this point. See laboratory manual al- 

 ready referred to (p. 387), exercise IX. 



469 



