436 



STRATIGRAPHICAL GEOLOGY 



Of Invertebrates very few new genera make their appearance 

 except among the Echinodermata and the Ammonoidea. The 

 Echinoderm genera Peltastes, Acrocidaris, Glypticus, Magnesia, and 

 Cyphosoma make their appearance. Among the Ammonoids many 

 of Middle Jurassic forms die out, while the following appear : 

 Aspidoceras, Cardioceras, Craspedites, Holcosteplianus, Peltoceras, 



Fig. 145. GROUP OF KIMERIDG1AN FOSSILS. 



a. Rhynchonella inconstans. <?. Thracia depressa. 



6. Exogyra virgula. e. Pleurotomaria reticulata. 



c. Astarte hartivellensis. /. Orbiculoidea latissima. 



g. Perisphinctes biplex. 



Polyptychites, and Ancyloceras. Of Dibranchiate Cephalopoda 

 Belemnoteuthis and Coccoteuthis are new. 



The following are some of the characteristic species of each 

 stage as developed in Northern Europe : 



Fossils of the Oxfordian 



B^achiopoda. Rhynchonella socialis, Waldheimia impressa. 



Lamellibranchia. Gryphaea dilatata, Pseudomonotis ovalis, Pecten 

 fibrosus, Pleuromya recurva, Anatina undulata, 

 Nucula ornata, Trigonia irregularis. 





