APPENDIX II 

 STRATIGRAPHICAL PALEONTOLOGY. 



I. GENERAL FEATURES OF 



OLDER PALAEOZOIC FAUNAS TAKEN 



AS A WHOLE. 



PRESENCE in abundance of Graptolites., Brachiopods, 

 and Trilobites ; in fair abundance of CORALS, CRINOIDS, 

 and CYSTIDS, NAUTILOIDEA (mainly straight or slightly 

 coiled). Rarity of Lamellibranchs and Gastropods. 

 Complete or almost complete absence of Echinids, 

 Ammonoidea, Vertebrata, and Plants. 



SPECIAL FAUNAL FEATURES OF THE SEPARATE 

 SYSTEMS. 



1. CAMBRIAN. Absence of Graptolites (except 

 in uppermost beds), Corals, Crinoids, and Cephalopods. 



BRACHIOPODS are mainly horny Inarticulata ; the 

 Orthids are the only other common forms. TRILOBITES 

 are micropygous (except Agnostus) ; they serve as zone- 

 fossils. The index-species of the Upper Cambrian are 

 mainly of the family Olenidtz, those of the Middle Cam- 

 brian, Paradoxidce, while Walcott's rather tentative 

 divisions of the Lower Cambrian are based on genera of 

 Mesonacidce. For details see p. 397. 



2. ORDOVICIAN. Abundance of branched Grap- 

 tolites, the most complexly branched being the earliest. 

 The Graptolites serve as zone-fossils (see p. 396), but are 

 almost confined to the black-shale facies. The Lower 

 Ordovician (Skiddavian-Llanvirnian) is characterized by 

 Dichograptids, the Upper by Leptograptids (Llandeilian), 

 Dicranograptids and Diplograptids. 



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