886 



MANUAL OF THE MOLLUSCA. 



Chonetes, Fischer. 



Example, C. striatella, PL XV., Fig. 29. 



Etymology, chone, a cup. 



Shell transversely oblong, with a wide and straight hinge- line ; 

 area double; valves radiately striated, articulated; hinge-margin 

 of ventral valve with a series of tub alar spines; fissure covered; 

 interior punctate-striate ; vascular impressions [v) very small. 

 (Davidson.) 



Fossil, 47 species. Silurian— Carboniferous. Europe, North 

 America, Falkland Islands. 



Dorsal valve. 



Fig. 192. 



Ventral valve. 



Family VI. — CuANiADiE. 



Shell orbicular, calcareous, hinge-less ; attached by the umbo, 

 or whole breadth of the ventral valve, rarely free ; dorsal valve 

 limpet-like ; interior of each valve with a broad granulated 

 border ; disk with four large muscular impressions, and digitated 

 vascular impressions ; structure punctate. 



Animal with free spiral arms, directed towards the concavity 

 of the dorsal valve, and supported by a nose-like prominence in 

 the middle of the lower valve ; mantle extending to the edges 

 of the valves, and closely adhering; its margins plain. 

 (Fig. 195.) 



Crania, Eetzius. 



Etymology, kraneia, capitate. 



Type, Anomia craniolaris, L. 



Examples, 0. Ignabergensis, PL XV., Fig. 30. C. anomala, 

 Figs. 193—195. 



Synonyms, Criopus, Poli. Orbicula (anomala), Cuvier, 

 -=0. Norvegica, Lam. 



* Interiors of two sp. of Chonetes, from Nehou and the Eifel, after Davidson : O, 

 adductor ; c, cardinals. 



