On the Cambrian Faunas of North America. Preliminary Studies

Acadian Geology Acrothele Agnostus Acadicus Agraulos angles of shield appears arched argillites backwards Baileyi Barrande Billingsi Bohemia border Braintree argillites Cambrian carapace cheek-lobes Conocephalites convex Corda costæ Crepicephalus curve Dawson Discina dorsal furrow elegans elevated Emmrichi Eteminicus facial sutures fixed cheeks flattened Formation and locality.-Cambrian frontal limb genus genus Ptychoparia Geol glabella glabellar furrows groove Hartt collection HARTTIA head Hist Hyolithes lamellatus length Linnarsson marginal fold Matthew Menevian Microdiscus punctatus middle N. S. Shaler narrow occipital furrow occipital ring ocular lobes ocular ridges operculum Orthis OUANGONDIANA outer Paradoxides beds Paradoxides Harlani Plate pleuræ posterior angles posterior margin Ptychoparia PTYCHOPARIA ORESTES Ptychoparia Robbi pygidium Ratcliff's Millstream Saint John fauna Saint John formation Saint John Group Salter Salteria segments shell Silur slightly Solenopleura South Braintree species spine striæ strongly convex surface sutures telson thorax transverse trilobite type specimen umbo ventral valve venulosa Whitfield width