10 



GASTEROPODA. 



Fiisus, distinguished by the spindle-shaped, many-whoiied 

 shell, and long straight canal (fig. 389), appears to have its 

 commencement in the Oolites. Species of Fusus become very 

 numerous towards the close of the Cretaceous period, and they 

 are very plentiful in the Tertiaries. One of the common fos- 



Fig. 3S9. — Fusus NeocmnieJisis. 

 Lower Greensand. 



Fig. 390. — Bnccinum undatum (var.) 

 Post-Pliocene and Recent. 



sils of the Eed Crag (Newer Pliocene) is the reversed shell, 

 Fusus contrarius (fig. 391, f), which is now known to exist 

 in the living state as well. 



The most ancient representative of the Muricidce, if rightly 

 referred here, is probably the genus Fusiqm'a (fig. 391, a), 

 of the Lower and Upper Silurian. In this genus the shell is 

 fusiform, wath an elevated spire, the mouth being elliptical 

 and produced below, and the columella twisted, but without 

 folds. 



Fa]\i. 3. BuccEsriD^. — Shell notched anteriorly, or with 

 the canal reflected, producing a kind of varix on the front 

 of the shell. With the exception of the extinct genus Fur- 

 purina of the Lower Oolites, and some species of Buccinum 

 in the Cretaceous rocks, the family of the Bucciniclm is ex- 

 clusively confined to the Tertiary and Eecent periods. The 

 two great families, therefore, of the Muricidcc and Buccinidm 

 are essentially characteristic of the later periods of the 



