306 



Monograph of the Gasteropoda. 



whorls of the spire ; animal usually too large for the shell ; foot wide, 

 oval ; operculum rudimentary, or none ; eyes on long pedicles at the 

 base of the tentacles ; mantle notched or perforated opposite the cor- 

 responding apertures in the edge of the shell, to admit the water to 

 the respiratory cavity when the animal is contracted ; pectinated 

 nearly equal. 



This family, among other genera, includes Murchisonia, Pleurotomaria, 

 Baphistomia. 



Genus Bellerophon — (Monfoet). 



\_Etym. — A fanciful ajipellation from Bellerophon, a fabulous hero 

 of Greece.] 



Shell symmetrical, involute, globose, or discoidally coiled, few 

 whorled ; whorls often sculptured ; sometimes dorsally keeled ; aper- 

 ture sinuated and deeply notched on the dorsal side. 



Bellerophon hilohatm — (Soweeby, 1839). 



Involute, subglobose, height and width about equal ; aperture bilo- 

 bate, large, subreuiform ; surface marked by fine stride, which, ascend- 

 ing from the umbilicus, form a broad arch on the side of the shell, and, 

 bending downward, meet in an abrupt curve on the dorsal Ime. 



It is exceedingly rare that the shell of this species is found in the 

 Cincinnati Group, but the casts are found at all elevations from low 

 water-mark to the Upper Silurian formation. The casts, too, are gen- 

 erally very unsatisfactory, and it can not be said they are particularly 

 abundant at any elevation. 



Bellerophon Mohri — (S. A. Millee). 



Fig. 30. Bellerophon 3Iohri.— This figure is unsatisfactory, because not sufficiently angulated, 



and appearing too much compressed. 



Shell involute; outer volution abruptly expanded at the aperture, 



