522 



MOLLUSCA 



PHYLUM VI 



Conradella U. and S. {Phragmolites Conrad) (Fig. 847, D, E). Ordovician and 

 Silurian. 



J -» 



E 



IV 



,? 



x^n 



Pio. 847. 



A, J!, Buamia hiiUl Ulr. and Scof. Ordovician ; Minnesota. C. S(tli>liiijostuma hndli (Wliitf.). Ordovician ; 

 Illinois. D, E, Conradella Jimbriata Ulr. and Scof. Ordovician ; Minnesota. 



Tetranota U. and S. Like Bucania, Init with four doi'sal ridges. Ordovician 

 and Silurian. 



Kokenia U. and S. Ordovician. Megalomphala Ulr. ; Oxydiscus Koken. 

 Ordovician to Devonian. 



Family 7. Bellerophontidae M'Coy. 



Symmetrical, involute sJiells ivith nqrldlij enlarginy wlturls, month expanded 

 laterally and ventrally but not dorsally ; umhilicus small or closed ; inner lip thickened, 

 outer with a short slit ; slit hand always present ; surface loith lines of growth only or 

 cancellated. Cambrian to Triassic. 



The Bellerophontidae were classed by Montfort with the Cephalopoda ; by Deshayes, 

 on account of their resemblance to Atlanta, with the Heteropoda ; and by de Koninck 



with the Aspidobranchiates. The 

 thick shells sometimes retain traces 

 of their original pigmentation. At 

 least 300 Paleozoic species have 

 l)een described. 



Bellerophon Montfort (Fig. 848). 

 Distinguished by : (1), the absence 

 of .sculpture save the lines of 

 growth ; (2) the small or entirely 

 closed umbilicus ; (3) the moderate 

 expanse of the aperture ; (4) the 

 callosity on the inner lip, and (5) 

 a well developed slit band terminat- 

 ing in a slit in the outer lip. Or- 

 dovician to Permian, maximum in Carboniferous. 



Patellosfimn Waagen. Like Bellerophon, but aperture greatly expanded. Devonian 

 and Carboniferous. 



Fi(!. 848. 



Bellerophon Hcarenux Leveille. Lower Carboniferous ; 

 Tournay, Belgium. 



