114 NEW YORK STATE MUSEUM 



Ordovician — Permian Cycloceras 



Silurian — Carboniferous Kionoceras, Protobactrites, Thoracoceras 



There are no persistent genera among the Ammonoidea and 

 Dibranchiata. 



The Trilobites contain a few persistent genera, namely: 



Ordovician — Devonian Goldius (Bronteus), Calymmene, Conolichas, 



Cyphaspis, Hoplolichas 

 Ordovician — Carboniferous . . Proetus 



The Branchiopoda contain : 



Devonian — Pleistocene Estheria 



Triassic — Recent Apus 



The Ostracoda have the following persistent genera : 



Ordovician — Devonian Beyrichia, Primitiella 



Ordovician — Carboniferous ..Aechmina, Bollia, Entomis, Leperditia, 



Ulrichia 



Ordovician — Permian Primitia 



Ordovician — Recent! Bairdia (maximum in Carboniferous), Bytho- 



cypris, Cypridina, Cytherella, Macrocypris 



Silurian — Recent! Poritocypris 



Permian — Recent! Cythere 



Jurassic — Recent Cytheridea 



Cretaceous — Recent Cythereis, Cytherideis 



The Cirripedia contain the following persistent genera: 

 Cambrian (?) — Devonian . . ..Turrilepas 



Ordovician — Devonian f . Lepidocoleus 



Cretaceous — Recent Chthamalus, Scalpellum 



The Malacostraca contain a small number of persistent types, 

 namely : 



Triassic — Cretaceous Glyphaea, Lithogaster 



Jurassic — Recent Callianassa 



Cretaceous — Recent Astacus (?), Homarus (?), Nephrops (?), 



Panopeus 



There are no arachnid (save the extinct Merostomata given 

 below), myriapod, or insect genera recorded as passing through 

 two or more formations. Among the Merostomata are : 



Ordovician — Devonian Pterygotus 



Ordovician — Permian Eurypterus 



Triassic — Recent Limulus 



Among the fishes the following Selachians are persistent: 



Triassic — Cretaceous Acrodus 



Jurassic — Recent Cestracion, Hybodus, Pristiurus, Rhinobates 



Cretaceous — Recent Acanthias, Callorhynchus, Carcharodon, Cen- 



trophorus, Lamna, Pristiophorus, Odon- 

 taspis, Raja, Scapanorhynchus, Scyllium, 

 Squatina 



