246 MOLLUSCA. GASTEROPODA 



crenulate internally. Columella truncated, provided with an oblique 

 fold in front. Upper Cretaceous to present day. Ex. JS r . mutabilis, 

 Pliocene and living. 



Chrysodomus ( = Neptunea). Shell solid, fusiform, spire 

 more or less elongate, sometimes sinistral. Aperture oval ; outer 

 lip simple ; inner lip smooth ; anterior canal short, slightly twisted. 

 Operculum horny, unguiculate. Eocene to present day. Ex. C. 

 antiquus, Red Crag to present day. 



Purpura. Shell tuberculate, striated or lamellar, without 

 varices. Spire rather short, last whorl large ; no umbilicus. Aper- 

 ture oval, large, with either an anterior notch or a short oblique 

 anterior canal, and a posterior notch or groove. Columella flattened, 

 with callus. Operculum lamellar, nucleus marginal. Miocene to 

 present day. Ex. P. persica, Recent ; P. lapillus, Red Crag to 

 present day. 



Murex. Shell thick, oval or elongate, spire prominent and 

 sharp ; whorls convex, each carrying three or more varices, which 

 may be spiny, foliaceous, or tubercular. Aperture ovate ; anterior 

 canal more or less long, narrow and tubular, often nearly closed ; 

 no posterior canal ; outer lip thick, inner lip smooth. Operculum 

 oval, nucleus sub -apical. Upper Cretaceous to present day. Ex. 

 M. brandaris, Recent ; M. frondosus, Barton Beds. 



Typhis. Similar to Murex ; small, with hollow spines ; 

 anterior canal short and completely closed. Upper Cretaceous to 

 present day. Ex. T. pungens, Barton Beds. 



Fusus. Shell without umbilicus, narrow, fusiform, elongate ; 

 spire sharp, with many whorls. Aperture oval ; outer lip simple, 

 thin, interior often striated. A long, straight, narrow anterior canal, 

 not closed. Columella smooth, without folds. Operculum oval. 

 Cretaceous to present day. Ex. F. colus, Recent ; F. porrectus, 

 Barton Beds. 



Clavella. Shell thick, usually large, fusiform, nearly smooth 

 (except the earlier whorls). Whorls often with a posterior carina 

 near the suture. Aperture pyriform, channelled posteriorly, with 

 a long straight anterior canal ; outer lip thickened posteriorly. 

 Last whorl contracting rapidly in front. Eocene to present day. 

 Ex. C. longceva, Barton Beds. 



