386 



MANUAL OF THE MOLLUSCA. 



Chonetes, Eisclier. 



Example, 0. striateUa, PI. 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 tubular 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 YI. — Chaniad^. 



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, 

 (Fig. 195.) 



and closely adhering; its margins plain. 



Cbania, Eetzius. 



Etymology, Jcraneia, capitate. 



Type, Anomia craniolaris, L. 



Examples, 0. Ignabergensis, PI. XY., Fig. 30. C. anomala, 

 Figs. 193—195. 



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

 _=0. Norvegica, Lam. 



* Interiors of two sp. of Ckonetes, from Nehou and the Eifel, after Davidson : 0, 

 adductor ; c, cardinals. 



