546 



HISTORICAL GEOLOGY. 



Atrypa reticularis, which continues on through the Devonian; Fig. 756, a 

 Chonetes — a genus of the Productus family. There were also species of 

 Orthoceras. 



Besides these, Figs. 759, 760 represent tracks probably of Mollusks, 

 The Cruziana (Eusophychus), called also Bilobites (Fig. 745), is a large 



751-760. 



751_^..,;...-,_ 759 



liSliiii 



DOTlIt '^ 





753 f-T\ 



MoLLrsKS. — Figs. 751, a, Fenestella prisea ; 752, Pentamerus oblongus ; 75^, a, part of casts of the interior ; 

 754, a, Atrypa reticularis ; 755, a, Hyattella congesta ; 756, Clionetes cornutus ; 757, Avicula rhomboidea ; 

 758, Cyclonema cancellatuin ; 759, track of a Lamellibranch (x^) ; 760, track of an Annelid ? (xj). Hall. 



species, the figure being reduced one half; other related kinds from the 

 Clinton are narrower, and six to eight inches long. 



The Cephalopods include OrtJioceras desideratum; also species of the 

 genus Discosorus of Hall, near Actinoceras in its broad beaded siphuncle^ 

 but having a shorter shell, more rapidly tapering and slightly curved ; the 

 species D. conoideus extends into the Niagara epoch. 



Trilobites occur of the genera Calymene, Dalmanites, Cerauriis, Illcenus, 

 Homalonotus and others, and some kinds are identical with ]*^iagara species. 



The remains of Fishes, reported from the Clinton beds of Pennsylvania, 

 are a small portion of a spine referred to a Shark, named by Claypole Onclius 

 Clintoni, together with fragments of what appear to be fish scales and plates. 

 The spines from British Upper Silurian beds, on which the genus Onclius 

 was established, are now regarded as portions of the telsons of species of 

 Cerati' icaris ; and the American may be of similar relations, but this is not 

 deemed probable. See under the Onondaga period, page 556. 



Remains of a Fish, Diplaspis Acadica Matthew (1888), are found at West- 

 field, in southern New Brunswick, in Silurian shales that underlie Niagara 

 beds, and are supposed to be of the Clinton group. The same beds contain. 

 " myriads " of the Ceratiocaris pusilla of Matthew. 



